gecko-dev/testing/modules/Assert.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// http://wiki.commonjs.org/wiki/Unit_Testing/1.0
// When you see a javadoc comment that contains a number, it's a reference to a
// specific section of the CommonJS spec.
//
// Originally from narwhal.js (http://narwhaljs.org)
// Copyright (c) 2009 Thomas Robinson <280north.com>
// MIT license: http://opensource.org/licenses/MIT

"use strict";

this.EXPORTED_SYMBOLS = [
  "Assert"
];

Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
Components.utils.import("resource://gre/modules/ObjectUtils.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "Promise",
                                  "resource://gre/modules/Promise.jsm");
/**
 * 1. The assert module provides functions that throw AssertionError's when
 * particular conditions are not met.
 *
 * To use the module you'll need to instantiate it first, which allows consumers
 * to override certain behavior on the newly obtained instance. For examples,
 * see the javadoc comments for the `report` member function.
 */
var Assert = this.Assert = function(reporterFunc) {
  if (reporterFunc)
    this.setReporter(reporterFunc);
};

function instanceOf(object, type) {
  return Object.prototype.toString.call(object) == "[object " + type + "]";
}

function replacer(key, value) {
  if (value === undefined) {
    return "" + value;
  }
  if (typeof value === "number" && (isNaN(value) || !isFinite(value))) {
    return value.toString();
  }
  if (typeof value === "function" || instanceOf(value, "RegExp")) {
    return value.toString();
  }
  return value;
}

const kTruncateLength = 128;

function truncate(text, newLength = kTruncateLength) {
  if (typeof text == "string") {
    return text.length < newLength ? text : text.slice(0, newLength);
  } else {
    return text;
  }
}

function getMessage(error, prefix = "") {
  let actual, expected;
  // Wrap calls to JSON.stringify in try...catch blocks, as they may throw. If
  // so, fall back to toString().
  try {
    actual = JSON.stringify(error.actual, replacer);
  } catch (ex) {
    actual = Object.prototype.toString.call(error.actual);
  }
  try {
    expected = JSON.stringify(error.expected, replacer);
  } catch (ex) {
    expected = Object.prototype.toString.call(error.expected);
  }
  let message = prefix;
  if (error.operator) {
    message += (prefix ? " - " : "") + truncate(actual) + " " + error.operator +
               " " + truncate(expected);
  }
  return message;
}

/**
 * 2. The AssertionError is defined in assert.
 *
 * Example:
 * new assert.AssertionError({
 *   message: message,
 *   actual: actual,
 *   expected: expected,
 *   operator: operator
 * });
 *
 * At present only the four keys mentioned above are used and
 * understood by the spec. Implementations or sub modules can pass
 * other keys to the AssertionError's constructor - they will be
 * ignored.
 */
Assert.AssertionError = function(options) {
  this.name = "AssertionError";
  this.actual = options.actual;
  this.expected = options.expected;
  this.operator = options.operator;
  this.message = getMessage(this, options.message);
  // The part of the stack that comes from this module is not interesting.
  let stack = Components.stack;
  do {
    stack = stack.asyncCaller || stack.caller;
  } while(stack && stack.filename && stack.filename.includes("Assert.jsm"))
  this.stack = stack;
};

// assert.AssertionError instanceof Error
Assert.AssertionError.prototype = Object.create(Error.prototype, {
  constructor: {
    value: Assert.AssertionError,
    enumerable: false,
    writable: true,
    configurable: true
  }
});

var proto = Assert.prototype;

proto._reporter = null;
/**
 * Set a custom assertion report handler function. Arguments passed in to this
 * function are:
 * err (AssertionError|null) An error object when the assertion failed or null
 *                           when it passed
 * message (string) Message describing the assertion
 * stack (stack) Stack trace of the assertion function
 *
 * Example:
 * ```js
 * Assert.setReporter(function customReporter(err, message, stack) {
 *   if (err) {
 *     do_report_result(false, err.message, err.stack);
 *   } else {
 *     do_report_result(true, message, stack);
 *   }
 * });
 * ```
 *
 * @param reporterFunc
 *        (function) Report handler function
 */
proto.setReporter = function(reporterFunc) {
  this._reporter = reporterFunc;
};

/**
 * 3. All of the following functions must throw an AssertionError when a
 * corresponding condition is not met, with a message that may be undefined if
 * not provided.  All assertion methods provide both the actual and expected
 * values to the assertion error for display purposes.
 *
 * This report method only throws errors on assertion failures, as per spec,
 * but consumers of this module (think: xpcshell-test, mochitest) may want to
 * override this default implementation.
 *
 * Example:
 * ```js
 * // The following will report an assertion failure.
 * this.report(1 != 2, 1, 2, "testing JS number math!", "==");
 * ```
 *
 * @param failed
 *        (boolean) Indicates if the assertion failed or not
 * @param actual
 *        (mixed) The result of evaluating the assertion
 * @param expected (optional)
 *        (mixed) Expected result from the test author
 * @param message (optional)
 *        (string) Short explanation of the expected result
 * @param operator (optional)
 *        (string) Operation qualifier used by the assertion method (ex: '==')
 */
proto.report = function(failed, actual, expected, message, operator) {
  let err = new Assert.AssertionError({
    message: message,
    actual: actual,
    expected: expected,
    operator: operator
  });
  if (!this._reporter) {
    // If no custom reporter is set, throw the error.
    if (failed) {
      throw err;
    }
  } else {
    this._reporter(failed ? err : null, err.message, err.stack);
  }
};

/**
 * 4. Pure assertion tests whether a value is truthy, as determined by !!guard.
 * assert.ok(guard, message_opt);
 * This statement is equivalent to assert.equal(true, !!guard, message_opt);.
 * To test strictly for the value true, use assert.strictEqual(true, guard,
 * message_opt);.
 *
 * @param value
 *        (mixed) Test subject to be evaluated as truthy
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.ok = function(value, message) {
  this.report(!value, value, true, message, "==");
};

/**
 * 5. The equality assertion tests shallow, coercive equality with ==.
 * assert.equal(actual, expected, message_opt);
 *
 * @param actual
 *        (mixed) Test subject to be evaluated as equivalent to `expected`
 * @param expected
 *        (mixed) Test reference to evaluate against `actual`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.equal = function equal(actual, expected, message) {
  this.report(actual != expected, actual, expected, message, "==");
};

/**
 * 6. The non-equality assertion tests for whether two objects are not equal
 * with != assert.notEqual(actual, expected, message_opt);
 *
 * @param actual
 *        (mixed) Test subject to be evaluated as NOT equivalent to `expected`
 * @param expected
 *        (mixed) Test reference to evaluate against `actual`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.notEqual = function notEqual(actual, expected, message) {
  this.report(actual == expected, actual, expected, message, "!=");
};

/**
 * 7. The equivalence assertion tests a deep equality relation.
 * assert.deepEqual(actual, expected, message_opt);
 *
 * We check using the most exact approximation of equality between two objects
 * to keep the chance of false positives to a minimum.
 * `JSON.stringify` is not designed to be used for this purpose; objects may
 * have ambiguous `toJSON()` implementations that would influence the test.
 *
 * @param actual
 *        (mixed) Test subject to be evaluated as equivalent to `expected`, including nested properties
 * @param expected
 *        (mixed) Test reference to evaluate against `actual`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.deepEqual = function deepEqual(actual, expected, message) {
  this.report(!ObjectUtils.deepEqual(actual, expected), actual, expected, message, "deepEqual");
};

/**
 * 8. The non-equivalence assertion tests for any deep inequality.
 * assert.notDeepEqual(actual, expected, message_opt);
 *
 * @param actual
 *        (mixed) Test subject to be evaluated as NOT equivalent to `expected`, including nested properties
 * @param expected
 *        (mixed) Test reference to evaluate against `actual`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.notDeepEqual = function notDeepEqual(actual, expected, message) {
  this.report(ObjectUtils.deepEqual(actual, expected), actual, expected, message, "notDeepEqual");
};

/**
 * 9. The strict equality assertion tests strict equality, as determined by ===.
 * assert.strictEqual(actual, expected, message_opt);
 *
 * @param actual
 *        (mixed) Test subject to be evaluated as strictly equivalent to `expected`
 * @param expected
 *        (mixed) Test reference to evaluate against `actual`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.strictEqual = function strictEqual(actual, expected, message) {
  this.report(actual !== expected, actual, expected, message, "===");
};

/**
 * 10. The strict non-equality assertion tests for strict inequality, as
 * determined by !==.  assert.notStrictEqual(actual, expected, message_opt);
 *
 * @param actual
 *        (mixed) Test subject to be evaluated as NOT strictly equivalent to `expected`
 * @param expected
 *        (mixed) Test reference to evaluate against `actual`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.notStrictEqual = function notStrictEqual(actual, expected, message) {
  this.report(actual === expected, actual, expected, message, "!==");
};

function expectedException(actual, expected) {
  if (!actual || !expected) {
    return false;
  }

  if (instanceOf(expected, "RegExp")) {
    return expected.test(actual);
  // We need to guard against the right hand parameter of "instanceof" lacking
  // the "prototype" property, which is true of arrow functions in particular.
  } else if (!(typeof expected === "function" && !expected.prototype) &&
             actual instanceof expected) {
    return true;
  } else if (expected.call({}, actual) === true) {
    return true;
  }

  return false;
}

/**
 * 11. Expected to throw an error:
 * assert.throws(block, Error_opt, message_opt);
 *
 * @param block
 *        (function) Function block to evaluate and catch eventual thrown errors
 * @param expected (optional)
 *        (mixed) Test reference to evaluate against the thrown result from `block`
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.throws = function(block, expected, message) {
  let actual;

  if (typeof expected === "string") {
    message = expected;
    expected = null;
  }

  try {
    block();
  } catch (e) {
    actual = e;
  }

  message = (expected && expected.name ? " (" + expected.name + ")." : ".") +
            (message ? " " + message : ".");

  if (!actual) {
    this.report(true, actual, expected, "Missing expected exception" + message);
  }

  if ((actual && expected && !expectedException(actual, expected))) {
    throw actual;
  }

  this.report(false, expected, expected, message);
};

/**
 * A promise that is expected to reject:
 * assert.rejects(promise, expected, message);
 *
 * @param promise
 *        (promise) A promise that is expected to reject
 * @param expected (optional)
 *        (mixed) Test reference to evaluate against the rejection result
 * @param message (optional)
 *        (string) Short explanation of the expected result
 */
proto.rejects = function(promise, expected, message) {
  return new Promise((resolve, reject) => {
    if (typeof expected === "string") {
      message = expected;
      expected = null;
    }
    return promise.then(
      () => this.report(true, null, expected, "Missing expected exception " + message),
      err => {
        if (expected && !expectedException(err, expected)) {
          reject(err);
          return;
        }
        this.report(false, err, expected, message);
        resolve();
      }
    ).then(null, reject);
  });
};

function compareNumbers(expression, lhs, rhs, message, operator) {
  let lhsIsNumber = typeof lhs == "number";
  let rhsIsNumber = typeof rhs == "number";

  if (lhsIsNumber && rhsIsNumber) {
    this.report(expression, lhs, rhs, message, operator);
    return;
  }

  let errorMessage;
  if (!lhsIsNumber && !rhsIsNumber) {
    errorMessage = "Neither '" + lhs + "' nor '" + rhs + "' are numbers";
  } else {
    errorMessage = "'" + (lhsIsNumber ? rhs : lhs) + "' is not a number";
  }
  this.report(true, lhs, rhs, errorMessage);
}

/**
 * The lhs must be greater than the rhs.
 * assert.greater(lhs, rhs, message_opt);
 *
 * @param lhs
 *        (number) The left-hand side value
 * @param rhs
 *        (number) The right-hand side value
 * @param message (optional)
 *        (string) Short explanation of the comparison result
 */
proto.greater = function greater(lhs, rhs, message) {
  compareNumbers.call(this, lhs <= rhs, lhs, rhs, message, ">");
};

/**
 * The lhs must be greater than or equal to the rhs.
 * assert.greaterOrEqual(lhs, rhs, message_opt);
 *
 * @param lhs
 *        (number) The left-hand side value
 * @param rhs
 *        (number) The right-hand side value
 * @param message (optional)
 *        (string) Short explanation of the comparison result
 */
proto.greaterOrEqual = function greaterOrEqual(lhs, rhs, message) {
  compareNumbers.call(this, lhs < rhs, lhs, rhs, message, ">=");
};

/**
 * The lhs must be less than the rhs.
 * assert.less(lhs, rhs, message_opt);
 *
 * @param lhs
 *        (number) The left-hand side value
 * @param rhs
 *        (number) The right-hand side value
 * @param message (optional)
 *        (string) Short explanation of the comparison result
 */
proto.less = function less(lhs, rhs, message) {
  compareNumbers.call(this, lhs >= rhs, lhs, rhs, message, "<");
};

/**
 * The lhs must be less than or equal to the rhs.
 * assert.lessOrEqual(lhs, rhs, message_opt);
 *
 * @param lhs
 *        (number) The left-hand side value
 * @param rhs
 *        (number) The right-hand side value
 * @param message (optional)
 *        (string) Short explanation of the comparison result
 */
proto.lessOrEqual = function lessOrEqual(lhs, rhs, message) {
  compareNumbers.call(this, lhs > rhs, lhs, rhs, message, "<=");
};