Assert

This module is used so that Ruff can test itself. It can be accessed with
require('assert').

assert.fail(actual, expected, message, operator)

Ruff available: v1.6.0

Throws an exception that displays the values for actual and expected
separated by the provided operator.

assert(value[, message]), assert.ok(value[, message])

Ruff available: v1.6.0

Tests if value is truthy. It is equivalent to
assert.equal(true, !!value, message).

assert.equal(actual, expected[, message])

Ruff available: v1.6.0

Tests shallow, coercive equality with the equal comparison operator ( == ).

assert.notEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests shallow, coercive inequality with the not equal comparison operator
( != ).

assert.deepEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests for deep equality. Primitive values are compared with the equal
comparison operator ( == ).

This only considers enumerable properties. It does not test object prototypes,
attached symbols, or non-enumerable properties. This can lead to some
potentially surprising results. For example, this does not throw an
AssertionError because the properties on the Error object are
non-enumerable:

// WARNING: This does not throw an AssertionError!
assert.deepEqual(Error('a'), Error('b'));

assert.notDeepEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests for any deep inequality. Opposite of assert.deepEqual.

assert.strictEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests strict equality as determined by the strict equality operator ( === ).

assert.notStrictEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests strict inequality as determined by the strict not equal operator
( !== ).

assert.deepStrictEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests for deep equality. Primitive values are compared with the strict equality
operator ( === ).

assert.notDeepStrictEqual(actual, expected[, message])

Ruff available: v1.6.0

Tests for deep inequality. Opposite of assert.deepStrictEqual.

assert.throws(block[, error][, message])

Ruff available: v1.6.0

Expects block to throw an error. error can be a constructor, RegExp, or
validation function.

Validate instanceof using constructor:

assert.throws(
  function() {
    throw new Error("Wrong value");
  },
  Error
);

Validate error message using RegExp:

assert.throws(
  function() {
    throw new Error("Wrong value");
  },
  /value/
);

Custom error validation:

assert.throws(
  function() {
    throw new Error("Wrong value");
  },
  function(err) {
    if ( (err instanceof Error) && /value/.test(err) ) {
      return true;
    }
  },
  "unexpected error"
);

assert.doesNotThrow(block[, error][, message])

Ruff available: v1.6.0

Expects block not to throw an error. See assert.throws() for more details.

If block throws an error and if it is of a different type from error, the
thrown error will get propagated back to the caller. The following call will
throw the TypeError, since we’re not matching the error types in the
assertion.

assert.doesNotThrow(
  function() {
    throw new TypeError("Wrong value");
  },
  SyntaxError
);

In case error matches with the error thrown by block, an AssertionError
is thrown instead.

assert.doesNotThrow(
  function() {
    throw new TypeError("Wrong value");
  },
  TypeError
);

assert.ifError(value)

Ruff available: v1.6.0

Throws value if value is truthy. This is useful when testing the error
argument in callbacks.