Actually fail tests when function in question does not throw error as expected

Actually fail tests when function in question does not throw error as expected

Fix #2790 (closed)

Added TestError which we can throw whenever we do the assert.fail(new TestError('...')); and then know it's the only special error we need to re-throw to fail the test.

const TestError = require('gitter-web-test-utils/lib/test-error');

try {
  someFunction();
  assert.fail(new TestError('expected error to be thrown'));
} catch (err) {
  if (err instanceof TestError) {
    throw err;
  }

  assert.ok(err);
}

Dev notes

Places of interest

• assert(err
• assert.ok(err
• assert.ok(false
• assert.fail(

Affected tests

• modules/cache-wrapper/test/cache-wrapper-test.js#L36-42
• modules/matrix-bridge/test/gitter-bridge-test.js
• modules/matrix-bridge/test/matrix-utils-test.js
• modules\matrix-bridge\test\matrix-event-handler-test.js
• Related but mis-use of assert.throws modules/gitlab/test/gitlab-user-service-test.js#L50-52