assert.alwaysThrew(spy, exception);

Like above, only required for all calls to the spy.

Passes, when the fake, spy or stub always threw the given exception.

The exception can be a String denoting its type, or an actual object.

When only one argument is provided, the assertion passes if spy always threw any exception.

import * as sinon from "sinon";
const f1 = sinon.fake();

f1("apple pie");

sinon.assert.alwaysThrew(f1, "TypeError");
// => Uncaught Error [AssertError]: fake did not throw exception

const f2 = sinon.fake.throws(new TypeError("not an apple pie"));

try {
  f2("apple pie");
} catch (err) {
  // not used
}

// Generates no error
sinon.assert.alwaysThrew(f2, "TypeError");

Example using test framework

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

tap.test("assert.alwaysThrew - passes when all calls threw", (t) => {
  const fake = sinon.fake.throws(new Error("boom"));

  try {
    fake();
  } catch (e) {}
  try {
    fake();
  } catch (e) {}

  t.doesNotThrow(() => {
    sinon.assert.alwaysThrew(fake);
  }, "assertion should pass when all calls threw");

  t.end();
});

tap.test("assert.alwaysThrew - fails when one call didn't throw", (t) => {
  const fake = sinon.fake();

  fake();

  t.throws(
    () => sinon.assert.alwaysThrew(fake),
    /fake did not always throw exception/,
    "assertion should fail when not all calls threw"
  );

  t.end();
});