Function constructorSpy

testing/mock.ts:720–754

Wraps a constructor with a Spy.

(
  constructor: new (...args: Args) => Self,
)

/** Wraps a constructor with a Spy. */
function constructorSpy<
  Self,
  Args extends unknown[],
>(
  constructor: new (...args: Args) => Self,
): ConstructorSpy<Self, Args> {
  const original = constructor;
  const calls: SpyCall<Self, Args, Self>[] = [];
  // @ts-ignore TS2509: Can't know the type of `original` statically.
  const spy = class extends original {
    // deno-lint-ignore constructor-super
    constructor(...args: Args) {
      const call: SpyCall<Self, Args, Self> = { args };
      try {
        super(...args);
        call.returned = this as unknown as Self;
      } catch (error) {
        call.error = error as Error;
        calls.push(call);
        throw error;
      }
      calls.push(call);
    }
    static readonly name = original.name;
    static readonly original = original;
    static readonly calls = calls;
    static readonly restored = false;
    static restore() {
      throw new MockError(
        "Cannot restore: constructor cannot be restored",
      );
    }
  } as ConstructorSpy<Self, Args>;
  return spy;
}

/**
 * Utility for extracting the arguments type from a property