diff --git a/fixtures/tbd/function.ts b/fixtures/input/function.ts
similarity index 100%
rename from fixtures/tbd/function.ts
rename to fixtures/input/function.ts
diff --git a/fixtures/output/function.d.ts b/fixtures/output/function.d.ts
new file mode 100644
index 0000000..2831bba
--- /dev/null
+++ b/fixtures/output/function.d.ts
@@ -0,0 +1,26 @@
+import type { BunPlugin } from 'bun';
+import type { DtsGenerationOption } from '@stacksjs/dtsx';
+export declare function fetchUsers(): Promise<ResponseData>;
+export declare function getProduct(id: number): Promise<ApiResponse<Product>>;
+export declare function authenticate(user: string, password: string): Promise<AuthResponse>;
+export declare function dts(options?: DtsGenerationOption): BunPlugin;
+declare const cwd: unknown;
+declare const c: unknown;
+declare const configPath: unknown;
+declare const importedConfig: unknown;
+declare const loadedConfig: unknown;
+export declare function processData(data: string): string;
+export declare function processData(data: number): number;
+export declare function processData(data: boolean): boolean;
+export declare function processData<T extends object>(data: T): T;
+export declare function processData(data: unknown): unknown;
+declare const results: unknown;
+export declare function isUser(value: unknown): value is User;
+export declare function extractFunctionSignature(declaration: string): FunctionSignature;
+declare const cleanDeclaration: unknown;
+declare const functionPattern: unknown;
+declare const functionMatch: unknown;
+declare const name: unknown;
+declare const genericsResult: unknown;
+declare const paramsResult: unknown;
+declare const match: unknown;
diff --git a/fixtures/tbd/class.ts b/fixtures/tbd/class.ts
deleted file mode 100644
index e54e93f..0000000
--- a/fixtures/tbd/class.ts
+++ /dev/null
@@ -1,11 +0,0 @@
-// TODO: Complex Error Handling
-// export class CustomError extends Error {
-//   constructor(
-//     message: string,
-//     public readonly code: number,
-//     public readonly metadata: Record<string, unknown>
-//   ) {
-//     super(message)
-//     this.name = 'CustomError'
-//   }
-// }
diff --git a/fixtures/wip/class.ts b/fixtures/wip/class.ts
new file mode 100644
index 0000000..ce12b47
--- /dev/null
+++ b/fixtures/wip/class.ts
@@ -0,0 +1,46 @@
+export class CustomError extends Error {
+  constructor(
+    message: string,
+    public readonly code: number,
+    public readonly metadata: Record<string, unknown>
+  ) {
+    super(message)
+    this.name = 'CustomError'
+  }
+}
+
+export class CustomErrorWithMethod extends CustomError {
+  logError() {
+    console.error(`[${this.code}] ${this.message}`)
+  }
+}
+
+export class CustomErrorWithMethodAndType extends CustomError {
+  logError(): void {
+    console.error(`[${this.code}] ${this.message}`)
+  }
+
+  getError(): Error {
+    return this
+  }
+}
+
+export class CustomErrorWithMethodAndTypeAndReturn {
+  constructor(
+    private message: string,
+    public readonly code: number,
+    public readonly metadata: Record<string, unknown>
+  ) {
+    this.message = message
+    this.code = code
+    this.metadata = metadata
+  }
+
+  logError(): void {
+    console.error(`[${this.code}] ${this.message}`)
+  }
+
+  getError(): Error {
+    return new Error(this.message)
+  }
+}
diff --git a/fixtures/tbd/enum.ts b/fixtures/wip/enum.ts
similarity index 100%
rename from fixtures/tbd/enum.ts
rename to fixtures/wip/enum.ts
diff --git a/fixtures/tbd/exports.ts b/fixtures/wip/exports.ts
similarity index 100%
rename from fixtures/tbd/exports.ts
rename to fixtures/wip/exports.ts
diff --git a/fixtures/tbd/interface.ts b/fixtures/wip/interface.ts
similarity index 100%
rename from fixtures/tbd/interface.ts
rename to fixtures/wip/interface.ts
diff --git a/fixtures/tbd/module.ts b/fixtures/wip/module.ts
similarity index 100%
rename from fixtures/tbd/module.ts
rename to fixtures/wip/module.ts
diff --git a/fixtures/tbd/type.ts b/fixtures/wip/type.ts
similarity index 100%
rename from fixtures/tbd/type.ts
rename to fixtures/wip/type.ts