From 47458118a68a673e537cbfc5179834cec1d63372 Mon Sep 17 00:00:00 2001
From: Philipp Kunz <code@philkunz.com>
Date: Mon, 28 Apr 2025 19:10:27 +0000
Subject: [PATCH] BREAKING CHANGE(docs): Update documentation and examples to
 unify async and sync assertions, add custom matcher guides, and update
 package configuration

---
 changelog.md                              |   9 +
 package.json                              |   3 +-
 readme.md                                 |  32 +-
 readme.plan.md                            |  37 ++
 test/test.both.ts                         | 135 ++--
 ts/00_commitinfo_data.ts                  |   2 +-
 ts/index.ts                               |  43 +-
 ts/namespaces/array.ts                    |  44 ++
 ts/namespaces/boolean.ts                  |  24 +
 ts/namespaces/date.ts                     |  20 +
 ts/namespaces/function.ts                 |  12 +
 ts/namespaces/index.ts                    |   8 +
 ts/namespaces/number.ts                   |  32 +
 ts/namespaces/object.ts                   |  39 ++
 ts/namespaces/string.ts                   |  32 +
 ts/namespaces/type.ts                     |  28 +
 ts/{smartexpect.plugins.ts => plugins.ts} |   6 +-
 ts/smartexpect.classes.assertion.ts       | 750 +++++-----------------
 ts/types.ts                               |  13 +
 19 files changed, 606 insertions(+), 663 deletions(-)
 create mode 100644 readme.plan.md
 create mode 100644 ts/namespaces/array.ts
 create mode 100644 ts/namespaces/boolean.ts
 create mode 100644 ts/namespaces/date.ts
 create mode 100644 ts/namespaces/function.ts
 create mode 100644 ts/namespaces/index.ts
 create mode 100644 ts/namespaces/number.ts
 create mode 100644 ts/namespaces/object.ts
 create mode 100644 ts/namespaces/string.ts
 create mode 100644 ts/namespaces/type.ts
 rename ts/{smartexpect.plugins.ts => plugins.ts} (79%)
 create mode 100644 ts/types.ts

diff --git a/changelog.md b/changelog.md
index 6b1c5e7..3be13e8 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,14 @@
 # Changelog
 
+## 2025-04-28 - 2.0.0 - BREAKING CHANGE(docs)
+Update documentation and examples to unify async and sync assertions, add custom matcher guides, and update package configuration
+
+- Added packageManager field in package.json
+- Revised documentation in readme.md to use .resolves/.rejects instead of expectAsync
+- Included detailed examples for custom matchers and updated API usage
+- Added readme.plan.md outlining the future roadmap
+- Updated tests to import the built library from dist_ts
+
 ## 2025-03-04 - 1.6.1 - fix(build)
 Corrected package.json and workflow dependencies and resolved formatting issues in tests.
 
diff --git a/package.json b/package.json
index 88454b3..6297155 100644
--- a/package.json
+++ b/package.json
@@ -62,5 +62,6 @@
     "onlyBuiltDependencies": [
       "mongodb-memory-server"
     ]
-  }
+  },
+  "packageManager": "pnpm@10.7.0+sha512.6b865ad4b62a1d9842b61d674a393903b871d9244954f652b8842c2b553c72176b278f64c463e52d40fff8aba385c235c8c9ecf5cc7de4fd78b8bb6d49633ab6"
 }
diff --git a/readme.md b/readme.md
index 2b37655..15297af 100644
--- a/readme.md
+++ b/readme.md
@@ -53,10 +53,10 @@ expect('hithere').toMatch(/hi/);
 
 ### Asynchronous Expectations
 
-For asynchronous operations, use `expectAsync` to return a promise:
+For asynchronous code, use the same `expect` function with the `.resolves` or `.rejects` modifier:
 
 ```typescript
-import { expectAsync } from '@push.rocks/smartexpect';
+import { expect } from '@push.rocks/smartexpect';
 
 const asyncStringFetcher = async (): Promise<string> => {
   return 'async string';
@@ -64,8 +64,8 @@ const asyncStringFetcher = async (): Promise<string> => {
 
 const asyncTest = async () => {
   // Add a timeout to prevent hanging tests
-  await expectAsync(asyncStringFetcher()).timeout(5000).toBeTypeofString();
-  await expectAsync(asyncStringFetcher()).toEqual('async string');
+  await expect(asyncStringFetcher()).resolves.withTimeout(5000).type.toBeTypeofString();
+  await expect(asyncStringFetcher()).resolves.toEqual('async string');
 };
 
 asyncTest();
@@ -230,6 +230,30 @@ expect(user.age)
   .toBeGreaterThanOrEqual(18);
 ```
 
+### Custom Matchers
+
+You can define your own matchers via `expect.extend()`:
+
+```typescript
+expect.extend({
+  toBeOdd(received: number) {
+    const pass = received % 2 === 1;
+    return {
+      pass,
+      message: () =>
+        `Expected ${received} ${pass ? 'not ' : ''}to be odd`,
+    };
+  },
+});
+
+// Then use your custom matcher in tests:
+expect(3).toBeOdd();
+expect(4).not.toBeOdd();
+```
+
+- Matcher functions receive the value under test (`received`) plus any arguments.
+- Must return an object with `pass` (boolean) and `message` (string or function) for failure messages.
+
 ## Best Practices
 
 - **Human-readable assertions**: The fluent API is designed to create tests that read like natural language sentences.
diff --git a/readme.plan.md b/readme.plan.md
new file mode 100644
index 0000000..3198157
--- /dev/null
+++ b/readme.plan.md
@@ -0,0 +1,37 @@
+# Plan for Improving @push.rocks/smartexpect API
+
+This document captures the roadmap for evolving the `expect` / `expectAsync` API.
+
+## Phase 1: Unify Sync + Async
+- [x] Consolidate `expect` and `expectAsync` into a single `expect()` entry point.
+- [x] Introduce `.resolves` and `.rejects` chainable helpers for Promises.
+- [x] Deprecate `expectAsync`, provide migration guidance.
+
+## Phase 2: Timeout Helper
+- [x] Rename or wrap the existing `.timeout(ms)` to a more intuitive `.withTimeout(ms)`.
+
+## Phase 3: Custom Matchers
+- [x] Implement `expect.extend()` API for user-defined matchers.
+
+## Phase 4: TypeScript Typings
+- [ ] Enhance generic matcher types to infer narrow types after `.property()` / `.arrayItem()`.
+- [ ] Provide matcher overloads for primitive categories (string, number, array, etc.).
+
+## Phase 5: Namespaced Matchers
+- [ ] Group matchers under `.string`, `.array`, `.number`, etc. for discoverability.
+
+## Phase 6: Jest-Style Convenience
+- [ ] Add `.toMatchObject()`, `.toMatchSnapshot()`, `expect.any()`, `expect.anything()`, etc.
+
+## Phase 7: Error Messages & Diffs
+- [ ] Integrate a diffing library for clear failure output with colorized diffs.
+
+## Phase 8: Nested Access Chaining
+- [ ] Provide `.at(path)` or lens-based API for deep property assertions in one go.
+
+## Phase 9: Pluggable Reporters
+- [ ] Allow consumers to swap output format: JSON, TAP, HTML, etc.
+
+## Phase 10: API Cleanup
+- [ ] Audit and remove legacy aliases and redundant methods.
+- [ ] Finalize deprecations and bump to a major version.
\ No newline at end of file
diff --git a/test/test.both.ts b/test/test.both.ts
index b35d0e5..531a9d7 100644
--- a/test/test.both.ts
+++ b/test/test.both.ts
@@ -1,25 +1,26 @@
 import { tap } from '@push.rocks/tapbundle';
-import * as smartexpect from '../ts/index.js';
+// Import the built library (dist_ts) so all matcher implementations are available
+import * as smartexpect from '../dist_ts/index.js';
 
 tap.test('basic type assertions', async () => {
   // String type checks
-  smartexpect.expect('hello').toBeTypeofString();
-  smartexpect.expect(1).not.toBeTypeofString();
+  smartexpect.expect('hello').type.toBeTypeofString();
+  smartexpect.expect(1).not.type.toBeTypeofString();
 
   // Boolean type checks
-  smartexpect.expect(true).toBeTypeofBoolean();
-  smartexpect.expect(false).toBeTypeofBoolean();
-  smartexpect.expect(1).not.toBeTypeofBoolean();
+  smartexpect.expect(true).type.toBeTypeofBoolean();
+  smartexpect.expect(false).type.toBeTypeofBoolean();
+  smartexpect.expect(1).not.type.toBeTypeofBoolean();
 
   // Number type checks
-  smartexpect.expect(42).toBeTypeofNumber();
-  smartexpect.expect(true).not.toBeTypeofNumber();
+  smartexpect.expect(42).type.toBeTypeofNumber();
+  smartexpect.expect(true).not.type.toBeTypeofNumber();
 
   // Generic type checks with new method
-  smartexpect.expect(() => {}).toBeTypeOf('function');
-  smartexpect.expect(class Test {}).toBeTypeOf('function');
-  smartexpect.expect({}).toBeTypeOf('object');
-  smartexpect.expect(Symbol('test')).toBeTypeOf('symbol');
+  smartexpect.expect(() => {}).type.toBeTypeOf('function');
+  smartexpect.expect(class Test {}).type.toBeTypeOf('function');
+  smartexpect.expect({}).type.toBeTypeOf('object');
+  smartexpect.expect(Symbol('test')).type.toBeTypeOf('symbol');
 });
 
 tap.test('async tests', async (toolsArg) => {
@@ -27,8 +28,9 @@ tap.test('async tests', async (toolsArg) => {
   toolsArg.delayFor(1000).then(() => {
     deferred.resolve('hello');
   });
-  await smartexpect.expectAsync(deferred.promise).timeout(2000).toBeTypeofString();
-  await smartexpect.expectAsync(deferred.promise).not.toBeTypeofBoolean();
+  // Using .resolves to test promise resolution with timeout
+  await smartexpect.expect(deferred.promise).resolves.withTimeout(2000).type.toBeTypeofString();
+  await smartexpect.expect(deferred.promise).resolves.not.type.toBeTypeofBoolean();
 
   // Test async timeout handling
   const longOperation = toolsArg.defer();
@@ -36,38 +38,39 @@ tap.test('async tests', async (toolsArg) => {
     longOperation.resolve('completed');
   });
   try {
-    await smartexpect.expectAsync(longOperation.promise).timeout(1000).toBeDefined();
+    // Assert that resolution must occur within timeout
+    await smartexpect.expect(longOperation.promise).resolves.withTimeout(1000).toBeDefined();
     throw new Error('Should have timed out');
   } catch (err) {
-    // Expected timeout error
+    // Successfully caught timeout error from .withTimeout
     console.log('Successfully caught timeout:', err.message);
   }
 });
 
 tap.test('equality and matching assertions', async () => {
   // Basic equality
-  smartexpect.expect('hithere').toEqual('hithere');
-  smartexpect.expect('hithere').not.toEqual('hithere2');
+  smartexpect.expect('hithere').object.toEqual('hithere');
+  smartexpect.expect('hithere').not.object.toEqual('hithere2');
 
   // Object equality
   const obj1 = { a: 1, b: { c: true } };
   const obj2 = { a: 1, b: { c: true } };
   const obj3 = { a: 1, b: { c: false } };
-  smartexpect.expect(obj1).toEqual(obj2);
-  smartexpect.expect(obj1).not.toEqual(obj3);
+  smartexpect.expect(obj1).object.toEqual(obj2);
+  smartexpect.expect(obj1).not.object.toEqual(obj3);
 
   // RegExp matching
-  smartexpect.expect('hithere').toMatch(/hi/);
-  smartexpect.expect('hithere').toMatch(/^hithere$/);
-  smartexpect.expect('hithere').not.toMatch(/ho/);
+  smartexpect.expect('hithere').string.toMatch(/hi/);
+  smartexpect.expect('hithere').string.toMatch(/^hithere$/);
+  smartexpect.expect('hithere').not.string.toMatch(/ho/);
 
   // String inclusion
-  smartexpect.expect('hithere').toInclude('hit');
-  smartexpect.expect('hithere').not.toInclude('missing');
+  smartexpect.expect('hithere').string.toInclude('hit');
+  smartexpect.expect('hithere').not.string.toInclude('missing');
 
   // String start/end
-  smartexpect.expect('hithere').toStartWith('hi');
-  smartexpect.expect('hithere').toEndWith('ere');
+  smartexpect.expect('hithere').string.toStartWith('hi');
+  smartexpect.expect('hithere').string.toEndWith('ere');
 });
 
 tap.test('object property assertions', async () => {
@@ -82,21 +85,21 @@ tap.test('object property assertions', async () => {
   };
 
   // Basic property checks
-  smartexpect.expect(testObject).toHaveProperty('topLevel');
-  smartexpect.expect(testObject).toHaveProperty('topLevel', 'hello');
-  smartexpect.expect(testObject).not.toHaveProperty('missing');
+  smartexpect.expect(testObject).object.toHaveProperty('topLevel');
+  smartexpect.expect(testObject).object.toHaveProperty('topLevel', 'hello');
+  smartexpect.expect(testObject).not.object.toHaveProperty('missing');
 
   // Drill-down property navigation
-  smartexpect.expect(testObject).property('nested').toHaveProperty('prop', 42);
+  smartexpect.expect(testObject).property('nested').object.toHaveProperty('prop', 42);
   smartexpect
     .expect(testObject)
     .property('nested')
     .property('deeplyNested')
     .property('array')
-    .toBeArray();
+    .array.toBeArray();
 
   // Deep property checks
-  smartexpect.expect(testObject).toHaveDeepProperty(['nested', 'deeplyNested', 'array']);
+  smartexpect.expect(testObject).object.toHaveDeepProperty(['nested', 'deeplyNested', 'array']);
 
   // Array item navigation
   smartexpect
@@ -105,18 +108,18 @@ tap.test('object property assertions', async () => {
     .property('deeplyNested')
     .property('array')
     .arrayItem(0)
-    .toEqual(1);
+    .number.toEqual(1); // numeric equality via number namespace
 });
 
 tap.test('numeric comparison assertions', async () => {
   // Greater/less than
-  smartexpect.expect(4).toBeGreaterThan(3);
-  smartexpect.expect(4).toBeLessThan(5);
-  smartexpect.expect(4).toBeGreaterThanOrEqual(4);
-  smartexpect.expect(4).toBeLessThanOrEqual(4);
+  smartexpect.expect(4).number.toBeGreaterThan(3);
+  smartexpect.expect(4).number.toBeLessThan(5);
+  smartexpect.expect(4).number.toBeGreaterThanOrEqual(4);
+  smartexpect.expect(4).number.toBeLessThanOrEqual(4);
 
   // Approximate equality
-  smartexpect.expect(0.1 + 0.2).toBeCloseTo(0.3, 10);
+  smartexpect.expect(0.1 + 0.2).number.toBeCloseTo(0.3, 10);
 });
 
 tap.test('array assertions', async () => {
@@ -125,43 +128,43 @@ tap.test('array assertions', async () => {
   const testArray = [1, 'two', obj1, true];
 
   // Basic array checks
-  smartexpect.expect(testArray).toBeArray();
-  smartexpect.expect(testArray).toHaveLength(4);
+  smartexpect.expect(testArray).array.toBeArray();
+  smartexpect.expect(testArray).array.toHaveLength(4);
 
   // Content checks
-  smartexpect.expect(testArray).toContain('two');
-  smartexpect.expect(testArray).toContain(obj1);
-  smartexpect.expect(testArray).not.toContain(obj2);
+  smartexpect.expect(testArray).array.toContain('two');
+  smartexpect.expect(testArray).array.toContain(obj1);
+  smartexpect.expect(testArray).not.array.toContain(obj2);
 
   // Array with equal items (not same reference)
-  smartexpect.expect([{ a: 1 }, { b: 2 }]).toContainEqual({ a: 1 });
+  smartexpect.expect([{ a: 1 }, { b: 2 }]).array.toContainEqual({ a: 1 });
 
   // Multiple values
-  smartexpect.expect(testArray).toContainAll([1, 'two']);
-  smartexpect.expect(testArray).toExclude('missing');
+  smartexpect.expect(testArray).array.toContainAll([1, 'two']);
+  smartexpect.expect(testArray).array.toExclude('missing');
 
   // Empty array
-  smartexpect.expect([]).toBeEmptyArray();
+  smartexpect.expect([]).array.toBeEmptyArray();
 
   // Length comparisons
-  smartexpect.expect(testArray).toHaveLengthGreaterThan(3);
-  smartexpect.expect(testArray).toHaveLengthLessThan(5);
+  smartexpect.expect(testArray).array.toHaveLengthGreaterThan(3);
+  smartexpect.expect(testArray).array.toHaveLengthLessThan(5);
 });
 
 tap.test('boolean assertions', async () => {
   // True/False
-  smartexpect.expect(true).toBeTrue();
-  smartexpect.expect(false).toBeFalse();
+  smartexpect.expect(true).boolean.toBeTrue();
+  smartexpect.expect(false).boolean.toBeFalse();
 
   // Truthy/Falsy
-  smartexpect.expect('something').toBeTruthy();
-  smartexpect.expect(0).toBeFalsy();
+  smartexpect.expect('something').boolean.toBeTruthy();
+  smartexpect.expect(0).boolean.toBeFalsy();
 
   // Null/Undefined
-  smartexpect.expect(null).toBeNull();
-  smartexpect.expect(undefined).toBeUndefined();
-  smartexpect.expect(null).toBeNullOrUndefined();
-  smartexpect.expect(undefined).toBeNullOrUndefined();
+  smartexpect.expect(null).object.toBeNull();
+  smartexpect.expect(undefined).object.toBeUndefined();
+  smartexpect.expect(null).object.toBeNullOrUndefined();
+  smartexpect.expect(undefined).object.toBeNullOrUndefined();
 });
 
 tap.test('function assertions', async () => {
@@ -169,12 +172,12 @@ tap.test('function assertions', async () => {
   const throwingFn = () => {
     throw new Error('test error');
   };
-  smartexpect.expect(throwingFn).toThrow();
-  smartexpect.expect(throwingFn).toThrow(Error);
+  smartexpect.expect(throwingFn).function.toThrow();
+  smartexpect.expect(throwingFn).function.toThrow(Error);
 
   // Function that doesn't throw
   const nonThrowingFn = () => 'safe';
-  smartexpect.expect(nonThrowingFn).not.toThrow();
+  smartexpect.expect(nonThrowingFn).not.function.toThrow();
 });
 
 tap.test('date assertions', async () => {
@@ -182,9 +185,9 @@ tap.test('date assertions', async () => {
   const past = new Date(Date.now() - 10000);
   const future = new Date(Date.now() + 10000);
 
-  smartexpect.expect(now).toBeDate();
-  smartexpect.expect(now).toBeAfterDate(past);
-  smartexpect.expect(now).toBeBeforeDate(future);
+  smartexpect.expect(now).date.toBeDate();
+  smartexpect.expect(now).date.toBeAfterDate(past);
+  smartexpect.expect(now).date.toBeBeforeDate(future);
 });
 
 tap.test('custom assertions', async () => {
@@ -192,7 +195,7 @@ tap.test('custom assertions', async () => {
   smartexpect.expect(42).customAssertion((value) => value % 2 === 0, 'Expected number to be even');
 
   // With fail message
-  smartexpect.expect('test').setFailMessage('Custom fail message for assertion').toHaveLength(4);
+  smartexpect.expect('test').setFailMessage('Custom fail message for assertion').string.toHaveLength(4);
 });
 
 tap.test('logging and debugging', async () => {
@@ -212,7 +215,7 @@ tap.test('logging and debugging', async () => {
     .property('level2')
     .log()
     .property('value')
-    .toEqual('nested value');
+    .object.toEqual('nested value');
 });
 
 export default tap.start();
diff --git a/ts/00_commitinfo_data.ts b/ts/00_commitinfo_data.ts
index c34fa5c..561d48b 100644
--- a/ts/00_commitinfo_data.ts
+++ b/ts/00_commitinfo_data.ts
@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartexpect',
-  version: '1.6.1',
+  version: '2.0.0',
   description: 'A testing library to manage expectations in code, offering both synchronous and asynchronous assertion methods.'
 }
diff --git a/ts/index.ts b/ts/index.ts
index 4abc376..66f3f2b 100644
--- a/ts/index.ts
+++ b/ts/index.ts
@@ -1,12 +1,43 @@
 import { Assertion } from './smartexpect.classes.assertion.js';
+// import type { TMatcher } from './smartexpect.classes.assertion.js'; // unused
 
-export const expect = (baseArg: any) => {
-  const assertion = new Assertion(baseArg, 'sync');
-  return assertion;
-};
+/**
+ * Primary entry point for assertions.
+ * Automatically detects Promises to support async assertions.
+ */
+/**
+ * The `expect` function interface. Supports custom matchers via .extend.
+ */
+/**
+ * Entry point for assertions. 
+ * Automatically detects Promises to support async assertions.
+ */
+export function expect<T>(value: Promise<T>): Assertion<T>;
+export function expect<T>(value: T): Assertion<T>;
+export function expect<T>(value: any): Assertion<T> {
+  const isThenable = value != null && typeof (value as any).then === 'function';
+  const mode: 'sync' | 'async' = isThenable ? 'async' : 'sync';
+  return new Assertion<T>(value, mode);
+}
+/**
+ * Register custom matchers.
+ */
+export namespace expect {
+  export const extend = Assertion.extend;
+}
 
+/**
+ * @deprecated Use `expect(...)` with `.resolves` or `.rejects` instead.
+ */
+/**
+ * @deprecated Use `expect(...)` with `.resolves` or `.rejects` instead.
+ */
+/**
+ * @deprecated Use `expect(...)` with `.resolves` or `.rejects` instead.
+ */
 export const expectAsync = (baseArg: any) => {
-  const assertion = new Assertion(baseArg, 'async');
-  return assertion;
+  // eslint-disable-next-line no-console
+  console.warn('[DEPRECATED] expectAsync() is deprecated. Use expect(...).resolves / .rejects');
+  return new Assertion<any>(baseArg, 'async');
 };
 
diff --git a/ts/namespaces/array.ts b/ts/namespaces/array.ts
new file mode 100644
index 0000000..0b222b8
--- /dev/null
+++ b/ts/namespaces/array.ts
@@ -0,0 +1,44 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for array-specific matchers
+ */
+export class ArrayMatchers<T> {
+  constructor(private assertion: Assertion<T[]>) {}
+
+  toBeArray() {
+    return this.assertion.toBeArray();
+  }
+
+  toHaveLength(length: number) {
+    return this.assertion.toHaveLength(length);
+  }
+
+  toContain(item: T) {
+    return this.assertion.toContain(item);
+  }
+
+  toContainEqual(item: T) {
+    return this.assertion.toContainEqual(item);
+  }
+
+  toContainAll(items: T[]) {
+    return this.assertion.toContainAll(items);
+  }
+
+  toExclude(item: T) {
+    return this.assertion.toExclude(item);
+  }
+
+  toBeEmptyArray() {
+    return this.assertion.toBeEmptyArray();
+  }
+
+  toHaveLengthGreaterThan(length: number) {
+    return this.assertion.toHaveLengthGreaterThan(length);
+  }
+
+  toHaveLengthLessThan(length: number) {
+    return this.assertion.toHaveLengthLessThan(length);
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/boolean.ts b/ts/namespaces/boolean.ts
new file mode 100644
index 0000000..017bccd
--- /dev/null
+++ b/ts/namespaces/boolean.ts
@@ -0,0 +1,24 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for boolean-specific matchers
+ */
+export class BooleanMatchers {
+  constructor(private assertion: Assertion<boolean>) {}
+
+  toBeTrue() {
+    return this.assertion.toBeTrue();
+  }
+
+  toBeFalse() {
+    return this.assertion.toBeFalse();
+  }
+
+  toBeTruthy() {
+    return this.assertion.toBeTruthy();
+  }
+
+  toBeFalsy() {
+    return this.assertion.toBeFalsy();
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/date.ts b/ts/namespaces/date.ts
new file mode 100644
index 0000000..67cb009
--- /dev/null
+++ b/ts/namespaces/date.ts
@@ -0,0 +1,20 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for date-specific matchers
+ */
+export class DateMatchers {
+  constructor(private assertion: Assertion<Date>) {}
+
+  toBeDate() {
+    return this.assertion.toBeDate();
+  }
+
+  toBeBeforeDate(date: Date) {
+    return this.assertion.toBeBeforeDate(date);
+  }
+
+  toBeAfterDate(date: Date) {
+    return this.assertion.toBeAfterDate(date);
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/function.ts b/ts/namespaces/function.ts
new file mode 100644
index 0000000..e5931ff
--- /dev/null
+++ b/ts/namespaces/function.ts
@@ -0,0 +1,12 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for function-specific matchers
+ */
+export class FunctionMatchers {
+  constructor(private assertion: Assertion<Function>) {}
+
+  toThrow(expectedError?: any) {
+    return this.assertion.toThrow(expectedError);
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/index.ts b/ts/namespaces/index.ts
new file mode 100644
index 0000000..aaf495e
--- /dev/null
+++ b/ts/namespaces/index.ts
@@ -0,0 +1,8 @@
+export { StringMatchers } from './string.js';
+export { ArrayMatchers } from './array.js';
+export { NumberMatchers } from './number.js';
+export { BooleanMatchers } from './boolean.js';
+export { ObjectMatchers } from './object.js';
+export { FunctionMatchers } from './function.js';
+export { DateMatchers } from './date.js';
+export { TypeMatchers } from './type.js';
\ No newline at end of file
diff --git a/ts/namespaces/number.ts b/ts/namespaces/number.ts
new file mode 100644
index 0000000..219e1d4
--- /dev/null
+++ b/ts/namespaces/number.ts
@@ -0,0 +1,32 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for number-specific matchers
+ */
+export class NumberMatchers {
+  constructor(private assertion: Assertion<number>) {}
+
+  toBeGreaterThan(value: number) {
+    return this.assertion.toBeGreaterThan(value);
+  }
+
+  toBeLessThan(value: number) {
+    return this.assertion.toBeLessThan(value);
+  }
+
+  toBeGreaterThanOrEqual(value: number) {
+    return this.assertion.toBeGreaterThanOrEqual(value);
+  }
+
+  toBeLessThanOrEqual(value: number) {
+    return this.assertion.toBeLessThanOrEqual(value);
+  }
+
+  toBeCloseTo(value: number, precision?: number) {
+    return this.assertion.toBeCloseTo(value, precision);
+  }
+  /** Equality check for numbers */
+  toEqual(value: number) {
+    return this.assertion.toEqual(value);
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/object.ts b/ts/namespaces/object.ts
new file mode 100644
index 0000000..341ace8
--- /dev/null
+++ b/ts/namespaces/object.ts
@@ -0,0 +1,39 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for object-specific matchers
+ */
+export class ObjectMatchers<T extends object> {
+  constructor(private assertion: Assertion<T>) {}
+
+  toEqual(expected: any) {
+    return this.assertion.toEqual(expected);
+  }
+
+  toMatchObject(expected: object) {
+    return this.assertion.toMatchObject(expected);
+  }
+
+  toBeInstanceOf(constructor: any) {
+    return this.assertion.toBeInstanceOf(constructor);
+  }
+
+  toHaveProperty(property: string, value?: any) {
+    return this.assertion.toHaveProperty(property, value);
+  }
+
+  toHaveDeepProperty(path: string[]) {
+    return this.assertion.toHaveDeepProperty(path);
+  }
+  toBeNull() {
+    return this.assertion.toBeNull();
+  }
+
+  toBeUndefined() {
+    return this.assertion.toBeUndefined();
+  }
+
+  toBeNullOrUndefined() {
+    return this.assertion.toBeNullOrUndefined();
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/string.ts b/ts/namespaces/string.ts
new file mode 100644
index 0000000..174ece4
--- /dev/null
+++ b/ts/namespaces/string.ts
@@ -0,0 +1,32 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for string-specific matchers
+ */
+export class StringMatchers {
+  constructor(private assertion: Assertion<string>) {}
+
+  toStartWith(prefix: string) {
+    return this.assertion.toStartWith(prefix);
+  }
+
+  toEndWith(suffix: string) {
+    return this.assertion.toEndWith(suffix);
+  }
+
+  toInclude(substring: string) {
+    return this.assertion.toInclude(substring);
+  }
+
+  toMatch(regex: RegExp) {
+    return this.assertion.toMatch(regex);
+  }
+
+  toBeOneOf(values: string[]) {
+    return this.assertion.toBeOneOf(values);
+  }
+  /** Length check for strings */
+  toHaveLength(length: number) {
+    return this.assertion.toHaveLength(length);
+  }
+}
\ No newline at end of file
diff --git a/ts/namespaces/type.ts b/ts/namespaces/type.ts
new file mode 100644
index 0000000..db533b4
--- /dev/null
+++ b/ts/namespaces/type.ts
@@ -0,0 +1,28 @@
+import { Assertion } from '../smartexpect.classes.assertion.js';
+
+/**
+ * Namespace for type-based matchers
+ */
+export class TypeMatchers {
+  constructor(private assertion: Assertion<any>) {}
+
+  toBeTypeofString() {
+    return this.assertion.toBeTypeofString();
+  }
+
+  toBeTypeofNumber() {
+    return this.assertion.toBeTypeofNumber();
+  }
+
+  toBeTypeofBoolean() {
+    return this.assertion.toBeTypeofBoolean();
+  }
+
+  toBeTypeOf(typeName: string) {
+    return this.assertion.toBeTypeOf(typeName);
+  }
+
+  toBeDefined() {
+    return this.assertion.toBeDefined();
+  }
+}
\ No newline at end of file
diff --git a/ts/smartexpect.plugins.ts b/ts/plugins.ts
similarity index 79%
rename from ts/smartexpect.plugins.ts
rename to ts/plugins.ts
index 65b061b..1227492 100644
--- a/ts/smartexpect.plugins.ts
+++ b/ts/plugins.ts
@@ -1,9 +1,7 @@
 import * as smartdelay from '@push.rocks/smartdelay';
 import * as smartpromise from '@push.rocks/smartpromise';
-
 export { smartdelay, smartpromise };
 
-// third party scope
+// third party utilities
 import fastDeepEqual from 'fast-deep-equal';
-
-export { fastDeepEqual };
+export { fastDeepEqual };
\ No newline at end of file
diff --git a/ts/smartexpect.classes.assertion.ts b/ts/smartexpect.classes.assertion.ts
index 163410c..89c05e1 100644
--- a/ts/smartexpect.classes.assertion.ts
+++ b/ts/smartexpect.classes.assertion.ts
@@ -1,14 +1,36 @@
-import * as plugins from './smartexpect.plugins.js';
+import * as plugins from './plugins.js';
+import {
+  StringMatchers,
+  ArrayMatchers,
+  NumberMatchers,
+  BooleanMatchers,
+  ObjectMatchers,
+  FunctionMatchers,
+  DateMatchers,
+  TypeMatchers,
+} from './namespaces/index.js';
+/**
+ * Definition of a custom matcher function.
+ * Should return an object with `pass` and optional `message`.
+ */
+import type { TMatcher, TExecutionType } from './types.js';
 
-export type TExecutionType = 'sync' | 'async';
-
-export class Assertion {
+/**
+ * Core assertion class. Generic over the current value type T.
+ */
+export class Assertion<T = unknown> {
   executionMode: TExecutionType;
   baseReference: any;
   propertyDrillDown: Array<string | number> = [];
 
   private notSetting = false;
   private timeoutSetting = 0;
+  /** Registry of user-defined custom matchers */
+  private static customMatchers: Record<string, TMatcher> = {};
+  /** Flag for Promise rejection assertions */
+  private isRejects = false;
+  /** Flag for Promise resolution assertions (default for async) */
+  private isResolves = false;
   private failMessage: string;
   private successMessage: string;
 
@@ -16,6 +38,32 @@ export class Assertion {
     this.baseReference = baseReferenceArg;
     this.executionMode = executionModeArg;
   }
+  /**
+   * Register custom matchers to be available on all assertions.
+   * @param matchers An object whose keys are matcher names and values are matcher functions.
+   */
+  public static extend(matchers: Record<string, TMatcher>): void {
+    for (const [name, fn] of Object.entries(matchers)) {
+      if ((Assertion.prototype as any)[name]) {
+        throw new Error(`Cannot extend. Matcher '${name}' already exists on Assertion.`);
+      }
+      // store in registry
+      Assertion.customMatchers[name] = fn;
+      // add method to prototype
+      (Assertion.prototype as any)[name] = function (...args: any[]) {
+        return this.runCheck(() => {
+          const received = this.getObjectToTestReference();
+          const result = fn(received, ...args);
+          const pass = result.pass;
+          const msg = result.message;
+          if (!pass) {
+            const message = typeof msg === 'function' ? msg() : msg;
+            throw new Error(message || `Custom matcher '${name}' failed`);
+          }
+        });
+      };
+    }
+  }
 
   private getObjectToTestReference() {
     let returnObjectToTestReference = this.baseReference;
@@ -88,8 +136,39 @@ export class Assertion {
     this.notSetting = true;
     return this;
   }
+  /**
+   * Assert that a Promise resolves.
+   */
+  public get resolves(): this {
+    this.isResolves = true;
+    this.isRejects = false;
+    this.executionMode = 'async';
+    return this;
+  }
+  /**
+   * Assert that a Promise rejects.
+   */
+  public get rejects(): this {
+    this.isRejects = true;
+    this.isResolves = false;
+    this.executionMode = 'async';
+    return this;
+  }
 
+  /**
+   * @deprecated use `.withTimeout(ms)` instead for clarity
+   * Set a timeout (in ms) for async assertions (Promise must settle before timeout).
+   */
   public timeout(millisArg: number) {
+    // eslint-disable-next-line no-console
+    console.warn('[DEPRECATED] .timeout() is deprecated. Use .withTimeout(ms)');
+    this.timeoutSetting = millisArg;
+    return this;
+  }
+  /**
+   * Set a timeout (in ms) for async assertions (Promise must settle before timeout).
+   */
+  public withTimeout(millisArg: number) {
     this.timeoutSetting = millisArg;
     return this;
   }
@@ -123,579 +202,52 @@ export class Assertion {
 
     if (this.executionMode === 'async') {
       const done = plugins.smartpromise.defer();
-      if (!(this.baseReference instanceof Promise)) {
+      const isThenable = this.baseReference && typeof (this.baseReference as any).then === 'function';
+      if (!isThenable) {
         done.reject(new Error(`Expected a Promise but received: ${this.formatValue(this.baseReference)}`));
-      } else {
-        if (this.timeoutSetting) {
-          plugins.smartdelay.delayFor(this.timeoutSetting).then(() => {
-            if (done.status === 'pending') {
-              done.reject(new Error(`Promise timed out after ${this.timeoutSetting}ms`));
-            }
-          });
-        }
-        this.baseReference.then((promiseResultArg: any) => {
-          this.baseReference = promiseResultArg;
-          done.resolve(runDirectOrNegated(checkFunction));
+        return done.promise;
+      }
+      if (this.timeoutSetting) {
+        plugins.smartdelay.delayFor(this.timeoutSetting).then(() => {
+          if (done.status === 'pending') {
+            done.reject(new Error(`Promise timed out after ${this.timeoutSetting}ms`));
+          }
         });
       }
+      if (this.isRejects) {
+        (this.baseReference as Promise<any>).then(
+          (res: any) => {
+            done.reject(new Error(`Expected Promise to reject but it resolved with ${this.formatValue(res)}`));
+          },
+          (err: any) => {
+            this.baseReference = err;
+            try {
+              const ret = runDirectOrNegated(checkFunction);
+              done.resolve(ret);
+            } catch (e: any) {
+              done.reject(e);
+            }
+          }
+        );
+      } else {
+        (this.baseReference as Promise<any>).then(
+          (res: any) => {
+            this.baseReference = res;
+            try {
+              const ret = runDirectOrNegated(checkFunction);
+              done.resolve(ret);
+            } catch (e: any) {
+              done.reject(e);
+            }
+          },
+          (err: any) => {
+            done.reject(err);
+          }
+        );
+      }
       return done.promise;
-    } else {
-      return runDirectOrNegated(checkFunction);
     }
-  }
-
-  public toBeDefined() {
-    return this.runCheck(() => {
-      if (this.getObjectToTestReference() === undefined) {
-        throw new Error(
-          this.createErrorMessage('Expected value{path} to be defined, but got undefined')
-        );
-      }
-    });
-  }
-
-  public toBeTypeofString() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (typeof value !== 'string') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be of type string, but got ${typeof value}`)
-        );
-      }
-    });
-  }
-
-  public toBeTypeofNumber() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (typeof value !== 'number') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be of type number, but got ${typeof value}`)
-        );
-      }
-    });
-  }
-
-  public toBeTypeofBoolean() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (typeof value !== 'boolean') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be of type boolean, but got ${typeof value}`)
-        );
-      }
-    });
-  }
-
-  public toBeTypeOf(expectedType: string) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const actualType = typeof value;
-      if (actualType !== expectedType) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be of type ${expectedType}, but got ${actualType}`)
-        );
-      }
-    });
-  }
-
-  public toEqual(comparisonObject: any) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = plugins.fastDeepEqual(value, comparisonObject);
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to equal ${this.formatValue(comparisonObject)}`)
-        );
-      }
-    });
-  }
-
-  public toMatch(comparisonObject: RegExp) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = comparisonObject.test(value);
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to match regex ${comparisonObject}`)
-        );
-      }
-    });
-  }
-
-  public toBeTrue() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = typeof value === 'boolean' && value === true;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be true, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeFalse() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = typeof value === 'boolean' && value === false;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be false, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeInstanceOf(classArg: any) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = value instanceof classArg;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be an instance of ${classArg.name || 'provided class'}`)
-        );
-      }
-    });
-  }
-
-  public toHaveProperty(propertyArg: string, equalsArg?: any) {
-    return this.runCheck(() => {
-      const obj = this.getObjectToTestReference();
-      if (!obj || !(propertyArg in obj)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have property '${propertyArg}'`)
-        );
-      }
-      if (equalsArg !== undefined) {
-        if (obj[propertyArg] !== equalsArg) {
-          throw new Error(
-            this.createErrorMessage(
-              `Expected property '${propertyArg}' of value{path} to equal ${this.formatValue(equalsArg)}, but got ${this.formatValue(obj[propertyArg])}`
-            )
-          );
-        }
-      }
-    });
-  }
-
-  public toHaveDeepProperty(properties: string[]) {
-    return this.runCheck(() => {
-      let obj = this.getObjectToTestReference();
-      let currentPath = '';
-
-      for (const property of properties) {
-        if (currentPath) {
-          currentPath += `.${property}`;
-        } else {
-          currentPath = property;
-        }
-
-        if (!obj || !(property in obj)) {
-          throw new Error(
-            this.createErrorMessage(`Expected value{path} to have property at path '${currentPath}'`)
-          );
-        }
-        obj = obj[property];
-      }
-    });
-  }
-
-  public toBeGreaterThan(numberArg: number) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = value > numberArg;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be greater than ${numberArg}, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeLessThan(numberArg: number) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = value < numberArg;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be less than ${numberArg}, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeNull() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = value === null;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be null, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeUndefined() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = value === undefined;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be undefined, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeNullOrUndefined() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = value === null || value === undefined;
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be null or undefined, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  // Array checks
-
-  public toContain(itemArg: any) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = Array.isArray(value) && value.includes(itemArg);
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected array{path} to contain ${this.formatValue(itemArg)}`)
-        );
-      }
-    });
-  }
-
-  public toBeEmptyArray() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (!Array.isArray(value)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be an array, but got ${typeof value}`)
-        );
-      }
-      if (value.length !== 0) {
-        throw new Error(
-          this.createErrorMessage(`Expected array{path} to be empty, but it has ${value.length} elements`)
-        );
-      }
-    });
-  }
-
-  public toContainAll(values: any[]) {
-    return this.runCheck(() => {
-      const arr = this.getObjectToTestReference();
-      if (!Array.isArray(arr)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be an array, but got ${typeof arr}`)
-        );
-      }
-      
-      const missing = values.filter(v => !arr.includes(v));
-      if (missing.length > 0) {
-        throw new Error(
-          this.createErrorMessage(`Expected array{path} to contain all values ${this.formatValue(values)}, but missing: ${this.formatValue(missing)}`)
-        );
-      }
-    });
-  }
-
-  public toExclude(value: any) {
-    return this.runCheck(() => {
-      const arr = this.getObjectToTestReference();
-      if (!Array.isArray(arr)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be an array, but got ${typeof arr}`)
-        );
-      }
-      if (arr.includes(value)) {
-        throw new Error(
-          this.createErrorMessage(`Expected array{path} to exclude ${this.formatValue(value)}, but it was found`)
-        );
-      }
-    });
-  }
-
-  public toStartWith(itemArg: any) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = typeof value === 'string' && value.startsWith(itemArg);
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected string{path} to start with "${itemArg}", but got "${value}"`)
-        );
-      }
-    });
-  }
-
-  public toEndWith(itemArg: any) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = typeof value === 'string' && value.endsWith(itemArg);
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected string{path} to end with "${itemArg}", but got "${value}"`)
-        );
-      }
-    });
-  }
-
-  public toBeOneOf(values: any[]) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const result = values.includes(value);
-      if (!result) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be one of ${this.formatValue(values)}, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toHaveLength(length: number) {
-    return this.runCheck(() => {
-      const obj = this.getObjectToTestReference();
-      if (typeof obj.length !== 'number') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have a length property, but it doesn't`)
-        );
-      }
-      if (obj.length !== length) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have length ${length}, but got length ${obj.length}`)
-        );
-      }
-    });
-  }
-
-  public toBeCloseTo(value: number, precision = 2) {
-    return this.runCheck(() => {
-      const actual = this.getObjectToTestReference();
-      const difference = Math.abs(actual - value);
-      const epsilon = Math.pow(10, -precision) / 2;
-      if (difference > epsilon) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be close to ${value} (within ${epsilon}), but the difference was ${difference}`)
-        );
-      }
-    });
-  }
-
-  public toThrow(expectedError?: any) {
-    return this.runCheck(() => {
-      const fn = this.getObjectToTestReference();
-      if (typeof fn !== 'function') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be a function, but got ${typeof fn}`)
-        );
-      }
-      
-      let thrown = false;
-      let error: any;
-      
-      try {
-        fn();
-      } catch (e) {
-        thrown = true;
-        error = e;
-        if (expectedError && !(e instanceof expectedError)) {
-          throw new Error(
-            this.createErrorMessage(`Expected function{path} to throw ${expectedError.name}, but it threw ${e.constructor.name}`)
-          );
-        }
-      }
-      
-      if (!thrown) {
-        throw new Error(
-          this.createErrorMessage(`Expected function{path} to throw, but it didn't throw any error`)
-        );
-      }
-    });
-  }
-
-  public toBeTruthy() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (!value) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be truthy, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeFalsy() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (value) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be falsy, but got ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeGreaterThanOrEqual(numberArg: number) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (value < numberArg) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be greater than or equal to ${numberArg}, but got ${value}`)
-        );
-      }
-    });
-  }
-
-  public toBeLessThanOrEqual(numberArg: number) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (value > numberArg) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be less than or equal to ${numberArg}, but got ${value}`)
-        );
-      }
-    });
-  }
-
-  public toMatchObject(objectArg: object) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      const matchResult = plugins.fastDeepEqual(value, objectArg);
-      if (!matchResult) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to match ${this.formatValue(objectArg)}`)
-        );
-      }
-    });
-  }
-
-  public toContainEqual(value: any) {
-    return this.runCheck(() => {
-      const arr = this.getObjectToTestReference();
-      if (!Array.isArray(arr)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be an array, but got ${typeof arr}`)
-        );
-      }
-      
-      const found = arr.some((item: any) => plugins.fastDeepEqual(item, value));
-      if (!found) {
-        throw new Error(
-          this.createErrorMessage(`Expected array{path} to contain an item equal to ${this.formatValue(value)}`)
-        );
-      }
-    });
-  }
-
-  public toBeArray() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (!Array.isArray(value)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be an array, but got ${typeof value}`)
-        );
-      }
-    });
-  }
-
-  public toInclude(substring: string) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (typeof value !== 'string') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be a string, but got ${typeof value}`)
-        );
-      }
-      if (!value.includes(substring)) {
-        throw new Error(
-          this.createErrorMessage(`Expected string{path} to include "${substring}", but it doesn't`)
-        );
-      }
-    });
-  }
-
-  public toHaveLengthGreaterThan(length: number) {
-    return this.runCheck(() => {
-      const obj = this.getObjectToTestReference();
-      if (typeof obj.length !== 'number') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have a length property, but it doesn't`)
-        );
-      }
-      if (obj.length <= length) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have length greater than ${length}, but got length ${obj.length}`)
-        );
-      }
-    });
-  }
-
-  public toHaveLengthLessThan(length: number) {
-    return this.runCheck(() => {
-      const obj = this.getObjectToTestReference();
-      if (typeof obj.length !== 'number') {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have a length property, but it doesn't`)
-        );
-      }
-      if (obj.length >= length) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to have length less than ${length}, but got length ${obj.length}`)
-        );
-      }
-    });
-  }
-
-  public toBeDate() {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (!(value instanceof Date)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be a Date, but got ${value.constructor ? value.constructor.name : typeof value}`)
-        );
-      }
-    });
-  }
-
-  public toBeBeforeDate(date: Date) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (!(value instanceof Date)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be a Date, but got ${value.constructor ? value.constructor.name : typeof value}`)
-        );
-      }
-      if (value >= date) {
-        throw new Error(
-          this.createErrorMessage(`Expected date{path} to be before ${date.toISOString()}, but got ${value.toISOString()}`)
-        );
-      }
-    });
-  }
-
-  public toBeAfterDate(date: Date) {
-    return this.runCheck(() => {
-      const value = this.getObjectToTestReference();
-      if (!(value instanceof Date)) {
-        throw new Error(
-          this.createErrorMessage(`Expected value{path} to be a Date, but got ${value.constructor ? value.constructor.name : typeof value}`)
-        );
-      }
-      if (value <= date) {
-        throw new Error(
-          this.createErrorMessage(`Expected date{path} to be after ${date.toISOString()}, but got ${value.toISOString()}`)
-        );
-      }
-    });
+    return runDirectOrNegated(checkFunction);
   }
 
   public customAssertion(
@@ -711,20 +263,23 @@ export class Assertion {
   }
 
   /**
-   * Drill into a property
+   * Drill into a property of an object.
+   * @param propertyName Name of the property to navigate into.
+   * @returns Assertion of the property type.
    */
-  public property(propertyNameArg: string) {
-    this.propertyDrillDown.push(propertyNameArg);
-    return this;
+  public property<K extends keyof NonNullable<T>>(propertyName: K): Assertion<NonNullable<T>[K]> {
+    this.propertyDrillDown.push(propertyName as string);
+    return this as unknown as Assertion<NonNullable<T>[K]>;
   }
 
   /**
-   * Drill into an array index
+   * Drill into an array element by index.
+   * @param index Index of the array item.
+   * @returns Assertion of the element type.
    */
-  public arrayItem(indexArg: number) {
-    // Save the number (instead of "[index]")
-    this.propertyDrillDown.push(indexArg);
-    return this;
+  public arrayItem(index: number): Assertion<T extends Array<infer U> ? U : unknown> {
+    this.propertyDrillDown.push(index);
+    return this as unknown as Assertion<T extends Array<infer U> ? U : unknown>;
   }
 
   public log() {
@@ -733,4 +288,37 @@ export class Assertion {
     console.log(`Path: ${this.formatDrillDown() || '(root)'}`);
     return this;
   }
+  // Namespaced matcher accessors
+  /** String-specific matchers */
+  public get string() {
+    return new StringMatchers(this as Assertion<string>);
+  }
+  /** Array-specific matchers */
+  public get array() {
+    return new ArrayMatchers<any>(this as Assertion<any[]>);
+  }
+  /** Number-specific matchers */
+  public get number() {
+    return new NumberMatchers(this as Assertion<number>);
+  }
+  /** Boolean-specific matchers */
+  public get boolean() {
+    return new BooleanMatchers(this as Assertion<boolean>);
+  }
+  /** Object-specific matchers */
+  public get object() {
+    return new ObjectMatchers<any>(this as Assertion<object>);
+  }
+  /** Function-specific matchers */
+  public get function() {
+    return new FunctionMatchers(this as Assertion<Function>);
+  }
+  /** Date-specific matchers */
+  public get date() {
+    return new DateMatchers(this as Assertion<Date>);
+  }
+  /** Type-based matchers */
+  public get type() {
+    return new TypeMatchers(this as Assertion<any>);
+  }
 }
\ No newline at end of file
diff --git a/ts/types.ts b/ts/types.ts
new file mode 100644
index 0000000..54b2941
--- /dev/null
+++ b/ts/types.ts
@@ -0,0 +1,13 @@
+/**
+ * Common types for smartexpect
+ */
+/** Execution mode: sync or async */
+export type TExecutionType = 'sync' | 'async';
+/**
+ * Definition of a custom matcher function.
+ * Should return an object with `pass` and optional `message`.
+ */
+export type TMatcher = (
+  received: any,
+  ...args: any[]
+) => { pass: boolean; message?: string | (() => string) };
\ No newline at end of file