How to expect optionally in jasmine. #Typescript solve: https://github.com/jasmine/jasmine/issues/1539

expectOptionally.ts

/**
 * Create an optional expectation for a spec.
 * @param actual Actual computed value to test expectations against.
 */
export function expectOptionally<T>(actual: any): jasmine.Matchers<T> {
  if (!isNullOrUndefined(actual)) {
    return expect(actual);
  }
  const voidExpect = new Proxy(expect(actual),
    {
      get: (target: any, prop) => {
        if (Object.keys(jasmine["matchers"]).indexOf(prop as string) !== -1) {
          return (actual: any, expected: any): jasmine.CustomMatcherResult => {
            let passed = true;
            target.addExpectationResult(passed, {
              matcherName: prop as String,
              passed,
              expected,
              actual,
              message: "Nothing to tell...",
              error: null
            });
            return;
          };
        }
        else
          return target[prop];
      }
    });
  return voidExpect as jasmine.Matchers<T>;
}