fix(assertion-matchers): Refactor matcher implementations to consistently use customAssertion for improved consistency and clarity.

ts/namespaces/function.ts

@@ -7,6 +7,23 @@ export class FunctionMatchers {
   constructor(private assertion: Assertion<Function>) {}
 
   toThrow(expectedError?: any) {
-    return this.assertion.toThrow(expectedError);
+    return this.assertion.customAssertion(
+      (value) => {
+        let threw = false;
+        try {
+          (value as Function)();
+        } catch (e: any) {
+          threw = true;
+          if (expectedError) {
+            if (typeof expectedError === 'function') {
+              return e instanceof expectedError;
+            }
+            return e === expectedError;
+          }
+        }
+        return threw;
+      },
+      `Expected function to throw${expectedError ? ` ${expectedError}` : ''}`
+    );
   }
 }