assert.fail(message)

This convenience method can cause a test library to fail a test.

Every assertion fails by calling this method.

import * as sinon from "sinon";
const msg = "Apple Pie";

sinon.assert.fail(msg);
// => Uncaught Error [AssertError]: Apple Pie

By default it throws an error of type sinon.assert.failException.

If the test framework looks for assertion errors by checking for a specific exception, you can override the kind of exception thrown. If that does not fit with your testing framework of choice, override the fail method to do the right thing.

Example using test framework

import tap from "tap";
import * as sinon from "sinon";

tap.test("assert.fail - throws with message", (t) => {
  t.throws(
    () => sinon.assert.fail("custom failure message"),
    /custom failure message/,
    "fail should throw with provided message"
  );

  t.end();
});

tap.test("assert.fail - throws AssertError", (t) => {
  try {
    sinon.assert.fail("test");
    t.fail("should have thrown");
  } catch (e) {
    t.equal(e.name, "AssertError", "error should be AssertError");
  }

  t.end();
});