Initial work on Dart bindings for Mojo.

mojo/public/dart/utils/lib/expect.dart

Index: mojo/public/dart/utils/lib/expect.dart
diff --git a/mojo/public/dart/utils/lib/expect.dart b/mojo/public/dart/utils/lib/expect.dart
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+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * This library contains an Expect class with static methods that can be used
+ * for simple unit-tests.
+ */
+library expect;
+
+/**
+ * Expect is used for tests that do not want to make use of the
+ * Dart unit test library - for example, the core language tests.
+ * Third parties are discouraged from using this, and should use
+ * the expect() function in the unit test library instead for
+ * test assertions.
+ */
+class Expect {
+  /**
+   * Return a slice of a string.
+   *
+   * The slice will contain at least the substring from [start] to the lower of
+   * [end] and `start + length`.
+   * If the result is no more than `length - 10` characters long,
+   * context may be added by extending the range of the slice, by decreasing
+   * [start] and increasing [end], up to at most length characters.
+   * If the start or end of the slice are not matching the start or end of
+   * the string, ellipses are added before or after the slice.
+   * Control characters may be encoded as "\xhh" codes.
+   */
+  static String _truncateString(String string, int start, int end, int length) {
+    if (end - start > length) {
+      end = start + length;
+    } else if (end - start < length) {
+      int overflow = length - (end - start);
+      if (overflow > 10) overflow = 10;
+      // Add context.
+      start = start - ((overflow + 1) ~/ 2);
+      end = end + (overflow ~/ 2);
+      if (start < 0) start = 0;
+      if (end > string.length) end = string.length;
+    }
+    if (start == 0 && end == string.length) return string;
+    StringBuffer buf = new StringBuffer();
+    if (start > 0) buf.write("...");
+    for (int i = start; i < end; i++) {
+      int code = string.codeUnitAt(i);
+      if (code < 0x20) {
+        buf.write(r"\x");
+        buf.write("0123456789abcdef"[code ~/ 16]);
+        buf.write("0123456789abcdef"[code % 16]);
+      } else {
+        buf.writeCharCode(string.codeUnitAt(i));
+      }
+    }
+    if (end < string.length) buf.write("...");
+    return buf.toString();
+  }
+
+  /**
+   * Find the difference between two strings.
+   *
+   * This finds the first point where two strings differ, and returns
+   * a text describing the difference.
+   *
+   * For small strings (length less than 20) nothing is done, and null is
+   * returned. Small strings can be compared visually, but for longer strings
+   * only a slice  containing the first difference will be shown.
+   */
+  static String _stringDifference(String expected, String actual) {
+    if (expected.length < 20 && actual.length < 20) return null;
+    for (int i = 0; i < expected.length && i < actual.length; i++) {
+      if (expected.codeUnitAt(i) != actual.codeUnitAt(i)) {
+        int start = i;
+        i++;
+        while (i < expected.length && i < actual.length) {
+          if (expected.codeUnitAt(i) == actual.codeUnitAt(i)) break;
+          i++;
+        }
+        int end = i;
+        var truncExpected = _truncateString(expected, start, end, 20);
+        var truncActual = _truncateString(actual, start, end, 20);
+        return "at index $start: Expected <$truncExpected>, "
+                                "Found: <$truncActual>";
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Checks whether the expected and actual values are equal (using `==`).
+   */
+  static void equals(var expected, var actual, [String reason = null]) {
+    if (expected == actual) return;
+    String msg = _getMessage(reason);
+    if (expected is String && actual is String) {
+      String stringDifference = _stringDifference(expected, actual);
+      if (stringDifference != null) {
+        _fail("Expect.equals($stringDifference$msg) fails.");
+      }
+    }
+    _fail("Expect.equals(expected: <$expected>, actual: <$actual>$msg) fails.");
+  }
+
+  /**
+   * Checks whether the actual value is a bool and its value is true.
+   */
+  static void isTrue(var actual, [String reason = null]) {
+    if (_identical(actual, true)) return;
+    String msg = _getMessage(reason);
+    _fail("Expect.isTrue($actual$msg) fails.");
+  }
+
+  /**
+   * Checks whether the actual value is a bool and its value is false.
+   */
+  static void isFalse(var actual, [String reason = null]) {
+    if (_identical(actual, false)) return;
+    String msg = _getMessage(reason);
+    _fail("Expect.isFalse($actual$msg) fails.");
+  }
+
+  /**
+   * Checks whether [actual] is null.
+   */
+  static void isNull(actual, [String reason = null]) {
+    if (null == actual) return;
+    String msg = _getMessage(reason);
+    _fail("Expect.isNull(actual: <$actual>$msg) fails.");
+  }
+
+  /**
+   * Checks whether [actual] is not null.
+   */
+  static void isNotNull(actual, [String reason = null]) {
+    if (null != actual) return;
+    String msg = _getMessage(reason);
+    _fail("Expect.isNotNull(actual: <$actual>$msg) fails.");
+  }
+
+  /**
+   * Checks whether the expected and actual values are identical
+   * (using `identical`).
+   */
+  static void identical(var expected, var actual, [String reason = null]) {
+    if (_identical(expected, actual)) return;
+    String msg = _getMessage(reason);
+    _fail("Expect.identical(expected: <$expected>, actual: <$actual>$msg) "
+          "fails.");
+  }
+
+  // Unconditional failure.
+  static void fail(String msg) {
+    _fail("Expect.fail('$msg')");
+  }
+
+  /**
+   * Failure if the difference between expected and actual is greater than the
+   * given tolerance. If no tolerance is given, tolerance is assumed to be the
+   * value 4 significant digits smaller than the value given for expected.
+   */
+  static void approxEquals(num expected,
+                           num actual,
+                           [num tolerance = null,
+                            String reason = null]) {
+    if (tolerance == null) {
+      tolerance = (expected / 1e4).abs();
+    }
+    // Note: use !( <= ) rather than > so we fail on NaNs
+    if ((expected - actual).abs() <= tolerance) return;
+
+    String msg = _getMessage(reason);
+    _fail('Expect.approxEquals(expected:<$expected>, actual:<$actual>, '
+          'tolerance:<$tolerance>$msg) fails');
+  }
+
+  static void notEquals(unexpected, actual, [String reason = null]) {
+    if (unexpected != actual) return;
+    String msg = _getMessage(reason);
+    _fail("Expect.notEquals(unexpected: <$unexpected>, actual:<$actual>$msg) "
+          "fails.");
+  }
+
+  /**
+   * Checks that all elements in [expected] and [actual] are equal `==`.
+   * This is different than the typical check for identity equality `identical`
+   * used by the standard list implementation.  It should also produce nicer
+   * error messages than just calling `Expect.equals(expected, actual)`.
+   */
+  static void listEquals(List expected, List actual, [String reason = null]) {
+    String msg = _getMessage(reason);
+    int n = (expected.length < actual.length) ? expected.length : actual.length;
+    for (int i = 0; i < n; i++) {
+      if (expected[i] != actual[i]) {
+        _fail('Expect.listEquals(at index $i, '
+              'expected: <${expected[i]}>, actual: <${actual[i]}>$msg) fails');
+      }
+    }
+    // We check on length at the end in order to provide better error
+    // messages when an unexpected item is inserted in a list.
+    if (expected.length != actual.length) {
+      _fail('Expect.listEquals(list length, '
+        'expected: <${expected.length}>, actual: <${actual.length}>$msg) '
+        'fails: Next element <'
+        '${expected.length > n ? expected[n] : actual[n]}>');
+    }
+  }
+
+  /**
+   * Checks that all [expected] and [actual] have the same set of keys (using
+   * the semantics of [Map.containsKey] to determine what "same" means. For
+   * each key, checks that the values in both maps are equal using `==`.
+   */
+  static void mapEquals(Map expected, Map actual, [String reason = null]) {
+    String msg = _getMessage(reason);
+
+    // Make sure all of the values are present in both and match.
+    for (final key in expected.keys) {
+      if (!actual.containsKey(key)) {
+        _fail('Expect.mapEquals(missing expected key: <$key>$msg) fails');
+      }
+
+      Expect.equals(expected[key], actual[key]);
+    }
+
+    // Make sure the actual map doesn't have any extra keys.
+    for (final key in actual.keys) {
+      if (!expected.containsKey(key)) {
+        _fail('Expect.mapEquals(unexpected key: <$key>$msg) fails');
+      }
+    }
+  }
+
+  /**
+   * Specialized equality test for strings. When the strings don't match,
+   * this method shows where the mismatch starts and ends.
+   */
+  static void stringEquals(String expected,
+                           String actual,
+                           [String reason = null]) {
+    String msg = _getMessage(reason);
+    String defaultMessage =
+        'Expect.stringEquals(expected: <$expected>", <$actual>$msg) fails';
+
+    if (expected == actual) return;
+    if ((expected == null) || (actual == null)) {
+      _fail('$defaultMessage');
+    }
+    // scan from the left until we find a mismatch
+    int left = 0;
+    int eLen = expected.length;
+    int aLen = actual.length;
+    while (true) {
+      if (left == eLen) {
+        assert (left < aLen);
+        String snippet = actual.substring(left, aLen);
+        _fail('$defaultMessage\nDiff:\n...[  ]\n...[ $snippet ]');
+        return;
+      }
+      if (left == aLen) {
+        assert (left < eLen);
+        String snippet = expected.substring(left, eLen);
+        _fail('$defaultMessage\nDiff:\n...[  ]\n...[ $snippet ]');
+        return;
+      }
+      if (expected[left] != actual[left]) {
+        break;
+      }
+      left++;
+    }
+
+    // scan from the right until we find a mismatch
+    int right = 0;
+    while (true) {
+      if (right == eLen) {
+        assert (right < aLen);
+        String snippet = actual.substring(0, aLen - right);
+        _fail('$defaultMessage\nDiff:\n[  ]...\n[ $snippet ]...');
+        return;
+      }
+      if (right == aLen) {
+        assert (right < eLen);
+        String snippet = expected.substring(0, eLen - right);
+        _fail('$defaultMessage\nDiff:\n[  ]...\n[ $snippet ]...');
+        return;
+      }
+      // stop scanning if we've reached the end of the left-to-right match
+      if (eLen - right <= left || aLen - right <= left) {
+        break;
+      }
+      if (expected[eLen - right - 1] != actual[aLen - right - 1]) {
+        break;
+      }
+      right++;
+    }
+    String eSnippet = expected.substring(left, eLen - right);
+    String aSnippet = actual.substring(left, aLen - right);
+    String diff = '\nDiff:\n...[ $eSnippet ]...\n...[ $aSnippet ]...';
+    _fail('$defaultMessage$diff');
+  }
+
+  /**
+   * Checks that every element of [expected] is also in [actual], and that
+   * every element of [actual] is also in [expected].
+   */
+  static void setEquals(Iterable expected,
+                        Iterable actual,
+                        [String reason = null]) {
+    final missingSet = new Set.from(expected);
+    missingSet.removeAll(actual);
+    final extraSet = new Set.from(actual);
+    extraSet.removeAll(expected);
+
+    if (extraSet.isEmpty && missingSet.isEmpty) return;
+    String msg = _getMessage(reason);
+
+    StringBuffer sb = new StringBuffer("Expect.setEquals($msg) fails");
+    // Report any missing items.
+    if (!missingSet.isEmpty) {
+      sb.write('\nExpected collection does not contain: ');
+    }
+
+    for (final val in missingSet) {
+      sb.write('$val ');
+    }
+
+    // Report any extra items.
+    if (!extraSet.isEmpty) {
+      sb.write('\nExpected collection should not contain: ');
+    }
+
+    for (final val in extraSet) {
+      sb.write('$val ');
+    }
+    _fail(sb.toString());
+  }
+
+  /**
+   * Calls the function [f] and verifies that it throws an exception.
+   * The optional [check] function can provide additional validation
+   * that the correct exception is being thrown.  For example, to check
+   * the type of the exception you could write this:
+   *
+   *     Expect.throws(myThrowingFunction, (e) => e is MyException);
+   */
+  static void throws(void f(),
+                     [_CheckExceptionFn check = null,
+                      String reason = null]) {
+    try {
+      f();
+    } catch (e, s) {
+      if (check != null) {
+        if (!check(e)) {
+          String msg = reason == null ? "" : reason;
+          _fail("Expect.throws($msg): Unexpected '$e'\n$s");
+        }
+      }
+      return;
+    }
+    String msg = reason == null ? "" : reason;
+    _fail('Expect.throws($msg) fails');
+  }
+
+  static String _getMessage(String reason)
+      => (reason == null) ? "" : ", '$reason'";
+
+  static void _fail(String message) {
+    throw new ExpectException(message);
+  }
+}
+
+bool _identical(a, b) => identical(a, b);
+
+typedef bool _CheckExceptionFn(exception);
+
+class ExpectException implements Exception {
+  ExpectException(this.message);
+  String toString() => message;
+  String message;
+}