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| 1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 library matcher.interfaces; |
| 6 |
| 7 // To decouple the reporting of errors, and allow for extensibility of |
| 8 // matchers, we make use of some interfaces. |
| 9 |
| 10 /// The ErrorFormatter type is used for functions that |
| 11 /// can be used to build up error reports upon [expect] failures. |
| 12 /// There is one built-in implementation ([defaultErrorFormatter]) |
| 13 /// which is used by the default failure handler. If the failure handler |
| 14 /// is replaced it may be desirable to replace the [stringDescription] |
| 15 /// error formatter with another. |
| 16 typedef String ErrorFormatter(actual, Matcher matcher, String reason, |
| 17 Map matchState, bool verbose); |
| 18 |
| 19 /// Matchers build up their error messages by appending to |
| 20 /// Description objects. This interface is implemented by |
| 21 /// StringDescription. This interface is unlikely to need |
| 22 /// other implementations, but could be useful to replace in |
| 23 /// some cases - e.g. language conversion. |
| 24 abstract class Description { |
| 25 int get length; |
| 26 |
| 27 /// Change the value of the description. |
| 28 Description replace(String text); |
| 29 |
| 30 /// This is used to add arbitrary text to the description. |
| 31 Description add(String text); |
| 32 |
| 33 /// This is used to add a meaningful description of a value. |
| 34 Description addDescriptionOf(value); |
| 35 |
| 36 /// This is used to add a description of an [Iterable] [list], |
| 37 /// with appropriate [start] and [end] markers and inter-element [separator]. |
| 38 Description addAll(String start, String separator, String end, Iterable list); |
| 39 } |
| 40 |
| 41 /// [expect] Matchers must implement/extend the Matcher class. |
| 42 /// The base Matcher class has a generic implementation of [describeMismatch] |
| 43 /// so this does not need to be provided unless a more clear description is |
| 44 /// required. The other two methods ([matches] and [describe]) |
| 45 /// must always be provided as they are highly matcher-specific. |
| 46 abstract class Matcher { |
| 47 const Matcher(); |
| 48 |
| 49 /// This does the matching of the actual vs expected values. |
| 50 /// [item] is the actual value. [matchState] can be supplied |
| 51 /// and may be used to add details about the mismatch that are too |
| 52 /// costly to determine in [describeMismatch]. |
| 53 bool matches(item, Map matchState); |
| 54 |
| 55 /// This builds a textual description of the matcher. |
| 56 Description describe(Description description); |
| 57 |
| 58 /// This builds a textual description of a specific mismatch. [item] |
| 59 /// is the value that was tested by [matches]; [matchState] is |
| 60 /// the [Map] that was passed to and supplemented by [matches] |
| 61 /// with additional information about the mismact, and [mismatchDescription] |
| 62 /// is the [Description] that is being built to decribe the mismatch. |
| 63 /// A few matchers make use of the [verbose] flag to provide detailed |
| 64 /// information that is not typically included but can be of help in |
| 65 /// diagnosing failures, such as stack traces. |
| 66 Description describeMismatch(item, Description mismatchDescription, |
| 67 Map matchState, bool verbose) => mismatchDescription; |
| 68 } |
| 69 |
| 70 /// Failed matches are reported using a default IFailureHandler. |
| 71 /// The default implementation simply throws [TestFailure]s; |
| 72 /// this can be replaced by some other implementation of |
| 73 /// IFailureHandler by calling configureExpectHandler. |
| 74 abstract class FailureHandler { |
| 75 /// This handles failures given a textual decription |
| 76 void fail(String reason); |
| 77 |
| 78 /// This handles failures given the actual [value], the [matcher] |
| 79 /// the [reason] (argument from [expect]), some additonal [matchState] |
| 80 /// generated by the [matcher], and a verbose flag which controls in |
| 81 /// some cases how much [matchState] information is used. It will use |
| 82 /// these to create a detailed error message (typically by calling |
| 83 /// an [ErrorFormatter]) and then call [fail] with this message. |
| 84 void failMatch(actual, Matcher matcher, String reason, |
| 85 Map matchState, bool verbose); |
| 86 } |
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