ruvnet/ruflo · error

Expected error to be instance of ${ErrorClass.name}, but got

Error message

Expected error to be instance of ${ErrorClass.name}, but got ${(error as Error).constructor.name}

What it means

expectToReject caught the rejection but the error's constructor did not match the expected ErrorClass. The operation did reject, just with the wrong error type — the message names both the expected and actual class so the mismatch is obvious.

Source

Thrown at v3/@claude-flow/testing/src/helpers/test-utils.ts:611

/**
 * Assert that a promise rejects with a specific error type
 *
 * @example
 * await expectToReject(
 *   async () => await riskyOperation(),
 *   ValidationError
 * );
 */
export async function expectToReject<T extends Error>(
  operation: () => Promise<unknown>,
  ErrorClass?: new (...args: unknown[]) => T
): Promise<T> {
  try {
    await operation();
    throw new Error('Expected operation to reject, but it resolved');
  } catch (error) {
    if (ErrorClass && !(error instanceof ErrorClass)) {
      throw new Error(
        `Expected error to be instance of ${ErrorClass.name}, but got ${(error as Error).constructor.name}`
      );
    }
    return error as T;
  }
}

/**
 * Create a mock function with tracking capabilities
 */
export function createTrackedMock<T extends (...args: unknown[]) => unknown>(
  implementation?: T
): TrackedMock<T> {
  // Use type assertion to handle the optional implementation
  const mock = implementation ? vi.fn(implementation) : vi.fn();
  const calls: Array<{ args: Parameters<T>; result?: ReturnType<T>; error?: Error; duration: number }> = [];

  const tracked = ((...args: Parameters<T>) => {

View on GitHub (pinned to fa13ee4ad6)

Solutions

1. Assert against the actual error class thrown, or fix the code to throw the expected class.
2. Wrap foreign errors in the expected error type at the boundary.

When it happens

Trigger: Thrown at v3/@claude-flow/testing/src/helpers/test-utils.ts:611 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of ruvnet/ruflo@fa13ee4ad6 (2026-08-18). Data as JSON: /api/errors/774b4358b1daccfc. Report an issue: GitHub.