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quiver/lib/testing/src/equality/equality.dart

-// Copyright 2014 Google Inc. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-part of quiver.testing.equality;
-
-/**
- * Matcher for == and hashCode methods of a class.
- *
- * To use, invoke areEqualityGroups with a list of equality groups where each
- * group contains objects that are supposed to be equal to each other, and
- * objects of different groups are expected to be unequal. For example:
- *
- *     expect({
- *      'hello': ["hello", "h" + "ello"],
- *      'world': ["world", "wor" + "ld"],
- *      'three': [2, 1 + 1]
- *     }, areEqualityGroups);
- *
- * This tests that:
- *
- * * comparing each object against itself returns true
- * * comparing each object against an instance of an incompatible class
- *     returns false
- * * comparing each pair of objects within the same equality group returns
- *     true
- * * comparing each pair of objects from different equality groups returns
- *     false
- * * the hash codes of any two equal objects are equal
- * * equals implementation is idempotent
- *
- * The format of the Map passed to expect is such that the map keys are used in
- * error messages to identify the group described by the map value.
- *
- * When a test fails, the error message labels the objects involved in
- * the failed comparison as follows:
- *
- *      "`[group x, item j]`" refers to the ith item in the xth equality group,
- *       where both equality groups and the items within equality groups are
- *       numbered starting from 1.  When either a constructor argument or an
- *       equal object is provided, that becomes group 1.
- *
- */
-const Matcher areEqualityGroups = const _EqualityGroupMatcher();
-
-const _repetitions = 3;
-
-class _EqualityGroupMatcher extends Matcher {
-  static const failureReason = 'failureReason';
-  const _EqualityGroupMatcher();
-
-  @override
-  Description describe(Description description) =>
-      description.add('to be equality groups');
-
-  @override
-  bool matches(Map<String, List> item, Map matchState) {
-    try {
-      _verifyEqualityGroups(item, matchState);
-      return true;
-    } on MatchError catch (e) {
-      matchState[failureReason] = e.toString();
-      return false;
-    }
-  }
-
-  Description describeMismatch(item, Description mismatchDescription,
-          Map matchState, bool verbose) =>
-      mismatchDescription.add(" ${matchState[failureReason]}");
-
-  void _verifyEqualityGroups(Map<String, List> equalityGroups, Map matchState) {
-    if (equalityGroups == null) {
-      throw new MatchError('Equality Group must not be null');
-    }
-    var equalityGroupsCopy = {};
-    equalityGroups.forEach((String groupName, List group) {
-      if (groupName == null) {
-        throw new MatchError('Group name must not be null');
-      }
-      if (group == null) {
-        throw new MatchError('Group must not be null');
-      }
-      equalityGroupsCopy[groupName] = new List.from(group);
-    });
-
-    // Run the test multiple times to ensure deterministic equals
-    for (var run in range(_repetitions)) {
-      _checkBasicIdentity(equalityGroupsCopy, matchState);
-      _checkGroupBasedEquality(equalityGroupsCopy);
-    }
-  }
-
-  void _checkBasicIdentity(Map<String, List> equalityGroups, Map matchState) {
-    var flattened = equalityGroups.values.expand((group) => group);
-    for (var item in flattened) {
-      if (item == _NotAnInstance.equalToNothing) {
-        throw new MatchError(
-            "$item must not be equal to an arbitrary object of another class");
-      }
-
-      if (item != item) {
-        throw new MatchError("$item must be equal to itself");
-      }
-
-      if (item.hashCode != item.hashCode) {
-        throw new MatchError("the implementation of hashCode of $item must "
-            "be idempotent");
-      }
-    }
-  }
-
-  void _checkGroupBasedEquality(Map<String, List> equalityGroups) {
-    equalityGroups.forEach((String groupName, List group) {
-      var groupLength = group.length;
-      for (var itemNumber = 0; itemNumber < groupLength; itemNumber++) {
-        _checkEqualToOtherGroup(
-            equalityGroups, groupLength, itemNumber, groupName);
-        _checkUnequalToOtherGroups(equalityGroups, groupName, itemNumber);
-      }
-    });
-  }
-
-  void _checkUnequalToOtherGroups(
-      Map<String, List> equalityGroups, String groupName, int itemNumber) {
-    equalityGroups.forEach((String unrelatedGroupName, List unrelatedGroup) {
-      if (groupName != unrelatedGroupName) {
-        for (var unrelatedItemNumber = 0;
-            unrelatedItemNumber < unrelatedGroup.length;
-            unrelatedItemNumber++) {
-          _expectUnrelated(equalityGroups, groupName, itemNumber,
-              unrelatedGroupName, unrelatedItemNumber);
-        }
-      }
-    });
-  }
-
-  void _checkEqualToOtherGroup(Map<String, List> equalityGroups,
-      int groupLength, int itemNumber, String groupName) {
-    for (var relatedItemNumber = 0;
-        relatedItemNumber < groupLength;
-        relatedItemNumber++) {
-      if (itemNumber != relatedItemNumber) {
-        _expectRelated(
-            equalityGroups, groupName, itemNumber, relatedItemNumber);
-      }
-    }
-  }
-
-  void _expectRelated(Map<String, List> equalityGroups, String groupName,
-      int itemNumber, int relatedItemNumber) {
-    var itemInfo = _createItem(equalityGroups, groupName, itemNumber);
-    var relatedInfo = _createItem(equalityGroups, groupName, relatedItemNumber);
-
-    if (itemInfo.value != relatedInfo.value) {
-      throw new MatchError("$itemInfo must be equal to $relatedInfo");
-    }
-
-    if (itemInfo.value.hashCode != relatedInfo.value.hashCode) {
-      throw new MatchError(
-          "the hashCode (${itemInfo.value.hashCode}) of $itemInfo must "
-          "be equal to the hashCode (${relatedInfo.value.hashCode}) of "
-          "$relatedInfo}");
-    }
-  }
-
-  void _expectUnrelated(Map<String, List> equalityGroups, String groupName,
-      int itemNumber, String unrelatedGroupName, int unrelatedItemNumber) {
-    var itemInfo = _createItem(equalityGroups, groupName, itemNumber);
-    var unrelatedInfo =
-        _createItem(equalityGroups, unrelatedGroupName, unrelatedItemNumber);
-
-    if (itemInfo.value == unrelatedInfo.value) {
-      throw new MatchError("$itemInfo must not be equal to " "$unrelatedInfo)");
-    }
-  }
-
-  _Item _createItem(
-          Map<String, List> equalityGroups, String groupName, int itemNumber) =>
-      new _Item(equalityGroups[groupName][itemNumber], groupName, itemNumber);
-}
-
-class _NotAnInstance {
-  static const equalToNothing = const _NotAnInstance._();
-  const _NotAnInstance._();
-}
-
-class _Item {
-  final Object value;
-  final String groupName;
-  final int itemNumber;
-
-  _Item(this.value, this.groupName, this.itemNumber);
-
-  @override
-  String toString() => "$value [group '$groupName', item ${itemNumber + 1}]";
-}
-
-class MatchError extends Error {
-  final message;
-
-  /// The [message] describes the match error.
-  MatchError([this.message]);
-
-  String toString() => message;
-}