How do I add a Jasmine custom matcher Typescript definition?
angular, jasmine, javascript, types, typescript
Solution
I had to modify three files when I added custom matchers. I created a file called matchers.ts that contained the actual matchers. I then added an import to test.ts for my matchers.ts file. Finally, I added an interface to the typings.d.ts file which contains my matcher.
matchers.ts (arbitrary name)
beforeEach(() => {
jasmine.addMatchers({
toContainText: () => {
return {
compare: (actual: HTMLElement, expectedText: string, customMessage?: string) => {
const actualText = actual.textContent;
return {
pass: actualText.indexOf(expectedText) > -1,
get message() {
let failureMessage = 'Expected ' + actualText + ' to contain ' + expectedText;
if (customMessage) {
failureMessage = ' ' + customMessage;
}
return failureMessage;
}
};
}
};
},
});
});
test.ts
import 'test/test-helpers/global/matchers'; (my relative filepath)
typings.d.ts
declare module jasmine {
interface Matchers {
toContainText(text: string, message?: string): boolean;
}
}
Problem
I've been looking around and this question seems like a recurring thing. However, none of the solutions I've found seem to work for me. Using the following: ``` { "typescript": "2.3.2", "jasmine-core": "2.6.1", "@types/jasmine": "2.5.47" } ``` I can't get Typescript to merge the namespace declaration containing my custom matcher definition. Adding this: ``` declare namespace jasmine { interface Matchers<T> { toBeAnyOf(expected: jasmine.Expected<T>, expectationFailOutput?: any): boolean; } } ``` Hides every other type previously declared on `jasmine`. Compiler outputs errors such as: ``` [ts] Namespace 'jasmine' has no exported member 'CustomMatcherFactories' [ts] Namespace 'jasmine' has no exported member 'CustomMatcher'. ``` Is there any proper way to add a custom matcher and make it play nicely with Typescript? There's an additional issue with `tslint` if you are using `tslint:recommended` ruleset. Those rules disallow the usage of `namespace` or `module` keywords, so I had to disable the linter (or change the `"no-namespace"` rule) in order to try this out. Unsure how one would get around extending definitions if this is "not recommended".