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Add rule to convert EqualTo(xxx) into Is.XXX
This is for: Is.EqualTo(false) => Is.False Is.EqualTo(true) => Is.True Is.EqualTo(null) => Is.Null Is.EqualTo(default) => Is.Default Apply suggestions from code review Co-authored-by: Mikkel Nylander Bundgaard <[email protected]>
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‎documentation/NUnit4002.md‎

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# NUnit4002
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## Use Specific constraint
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| Topic | Value
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| :-- | :--
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| Id | NUnit4002
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| Severity | Info
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| Enabled | True
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| Category | Style
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| Code | [UseSpecificConstraintAnalyzer](https://github.com/nunit/nunit.analyzers/blob/master/src/nunit.analyzers/UseSpecificConstraint/UseSpecificConstraintAnalyzer.cs)
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## Description
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Replace 'EqualTo' with a keyword in the corresponding specific constraint.
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## Motivation
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Sometimes constraints can be written more concisely using the inbuilt constraints provided by NUnit -
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e.g. `Is.True` instead of `Is.EqualTo(true)`.
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Also, from NUnit version 4.3.0 where new overloads of `Is.EqualTo` were introduced, it is sometimes
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not possible to uniquely determine `default` when provided as the expected value - e.g. in
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`Is.EqualTo(default)`. Again, in such cases, it is better to use the inbuilt constraint provided by NUnit.
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Some examples of constraints that can be be simplified by using a more specific constraint can be seen below.
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```csharp
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[Test]
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public void Test()
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{
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Assert.That(actualFalse, Is.EqualTo(false));
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Assert.That(actualTrue, Is.EqualTo(true));
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Assert.That(actualObject, Is.EqualTo(null));
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Assert.That(actualObject, Is.EqualTo(default));
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Assert.That(actualInt, Is.EqualTo(default));
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}
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## How to fix violations
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The analyzer comes with a code fix that will replace the constraint `Is.EqualTo(x)` with
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the matching `Is.X` constraint (for some `x`). So the code block above will be changed into
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```csharp
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[Test]
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public void Test()
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{
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Assert.That(actualFalse, Is.False);
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Assert.That(actualTrue, Is.True);
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Assert.That(actualObject, Is.Null);
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Assert.That(actualObject, Is.Null);
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Assert.That(actualInt, Is.Default);
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}
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<!-- start generated config severity -->
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## Configure severity
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### Via ruleset file
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Configure the severity per project, for more info see
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[MSDN](https://learn.microsoft.com/en-us/visualstudio/code-quality/using-rule-sets-to-group-code-analysis-rules?view=vs-2022).
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### Via .editorconfig file
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```ini
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# NUnit4002: Use Specific constraint
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dotnet_diagnostic.NUnit4002.severity = chosenSeverity
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```
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where `chosenSeverity` can be one of `none`, `silent`, `suggestion`, `warning`, or `error`.
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### Via #pragma directive
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```csharp
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#pragma warning disable NUnit4002 // Use Specific constraint
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Code violating the rule here
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#pragma warning restore NUnit4002 // Use Specific constraint
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```
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Or put this at the top of the file to disable all instances.
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```csharp
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#pragma warning disable NUnit4002 // Use Specific constraint
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```
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### Via attribute `[SuppressMessage]`
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```csharp
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[System.Diagnostics.CodeAnalysis.SuppressMessage("Style",
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"NUnit4002:Use Specific constraint",
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Justification = "Reason...")]
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```
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<!-- end generated config severity -->

‎documentation/index.md‎

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@@ -132,4 +132,5 @@ Rules which help you write concise and readable NUnit test code.
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| Id | Title | :mag: | :memo: | :bulb: |
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| :-- | :-- | :--: | :--: | :--: |
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| [NUnit4001](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit4001.md) | Simplify the Values attribute | :white_check_mark: | :information_source: | :x: |
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| [NUnit4001](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit4001.md) | Simplify the Values attribute | :white_check_mark: | :information_source: | :white_check_mark: |
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| [NUnit4002](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit4002.md) | Use Specific constraint | :white_check_mark: | :information_source: | :white_check_mark: |

‎src/nunit.analyzers.codefixes/UseSpecificConstraint/UseSpecificConstraintCodeFix.cs‎

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using System.Collections.Immutable;
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using System.Composition;
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using System.Linq;
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using System.Threading.Tasks;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.CodeActions;
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using Microsoft.CodeAnalysis.CodeFixes;
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using Microsoft.CodeAnalysis.CSharp;
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using Microsoft.CodeAnalysis.CSharp.Syntax;
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using NUnit.Analyzers.Constants;
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using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
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namespace NUnit.Analyzers.UseSpecificConstraint
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{
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[ExportCodeFixProvider(LanguageNames.CSharp)]
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[Shared]
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internal class UseSpecificConstraintCodeFix : CodeFixProvider
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{
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internal const string UseSpecificConstraint = "Use specific constraint";
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public override ImmutableArray<string> FixableDiagnosticIds { get; } = ImmutableArray.Create(
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AnalyzerIdentifiers.UseSpecificConstraint);
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public sealed override FixAllProvider GetFixAllProvider()
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{
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return WellKnownFixAllProviders.BatchFixer;
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}
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public override async Task RegisterCodeFixesAsync(CodeFixContext context)
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{
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SyntaxNode? root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
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if (root is null)
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{
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return;
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}
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context.CancellationToken.ThrowIfCancellationRequested();
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SyntaxNode node = root.FindNode(context.Span);
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if (node is ArgumentSyntax argument)
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{
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node = argument.Expression;
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}
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if (node is not InvocationExpressionSyntax originalExpression ||
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originalExpression.Expression is not MemberAccessExpressionSyntax memberAccessExpression)
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{
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return;
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}
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var diagnostic = context.Diagnostics.First();
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var constraint = diagnostic.Properties[AnalyzerPropertyKeys.SpecificConstraint]!;
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var newExpression = MemberAccessExpression(
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SyntaxKind.SimpleMemberAccessExpression,
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memberAccessExpression.Expression,
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IdentifierName(constraint));
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SyntaxNode newRoot = root.ReplaceNode(originalExpression, newExpression);
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var codeAction = CodeAction.Create(
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UseSpecificConstraint,
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_ => Task.FromResult(context.Document.WithSyntaxRoot(newRoot)),
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UseSpecificConstraint);
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context.RegisterCodeFix(codeAction, context.Diagnostics);
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}
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}
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}

‎src/nunit.analyzers.tests/DocumentationTests.cs‎

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[TestCase(Categories.Structure, 0)]
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[TestCase(Categories.Assertion, 1)]
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[TestCase(Categories.Style, 2)]
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[TestCase(Categories.Style, 3)]
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public void EnsureThatAnalyzerIndexIsAsExpected(string category, int tableNumber)
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{
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var builder = new StringBuilder();

‎src/nunit.analyzers.tests/UseSpecificConstraint/UseSpecificConstraintAnalyzerTests.cs‎

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using Gu.Roslyn.Asserts;
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using Microsoft.CodeAnalysis.Diagnostics;
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using NUnit.Analyzers.Constants;
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using NUnit.Analyzers.UseSpecificConstraint;
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using NUnit.Framework;
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namespace NUnit.Analyzers.Tests.UseSpecificConstraint
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{
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public class UseSpecificConstraintAnalyzerTests
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{
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private static readonly DiagnosticAnalyzer analyzer = new UseSpecificConstraintAnalyzer();
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private static readonly ExpectedDiagnostic expectedDiagnostic =
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ExpectedDiagnostic.Create(AnalyzerIdentifiers.UseSpecificConstraint);
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private static readonly string[][] EqualToSpecificConstraint =
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[
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["false", "False"],
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#if NUNIT4
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["default(bool)", "Default"],
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#else
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["default(bool)", "False"],
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#endif
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["true", "True"],
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["null", "Null"],
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["default(object)", "Null"],
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["default(string)", "Null"],
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#if NUNIT4
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["default(int)", "Default"],
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#endif
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];
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[TestCaseSource(nameof(EqualToSpecificConstraint))]
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public void AnalyzeForSpecificConstraint(string literal, string constraint) => AnalyzeForEqualTo(literal, constraint);
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#if NUNIT4
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[Test]
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public void AnalyzeForIsDefault() => AnalyzeForEqualTo("default", "Default",
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Settings.Default.WithAllowedCompilerDiagnostics(AllowedCompilerDiagnostics.WarningsAndErrors));
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#endif
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private static void AnalyzeForEqualTo(string literal, string constraint, Settings? settings = null)
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{
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AnalyzeForEqualTo("Is", string.Empty, literal, constraint, settings);
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AnalyzeForEqualTo("Is", ".And.Not.Empty", literal, constraint, settings);
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AnalyzeForEqualTo("Is.Not", string.Empty, literal, constraint, settings);
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AnalyzeForEqualTo("Is.EqualTo(0).Or", string.Empty, literal, constraint, settings);
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}
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private static void AnalyzeForEqualTo(string prefix, string suffix, string literal, string constraint, Settings? settings = null)
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{
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var testCode = TestUtility.WrapInTestMethod(
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$"Assert.That(false, ↓{prefix}.EqualTo({literal}){suffix});");
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RoslynAssert.Diagnostics(analyzer,
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expectedDiagnostic.WithMessage($"Replace 'Is.EqualTo({literal})' with 'Is.{constraint}' constraint"),
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testCode, settings);
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}
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}
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}

‎src/nunit.analyzers.tests/UseSpecificConstraint/UseSpecificConstraintCodeFixTests.cs‎

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using Gu.Roslyn.Asserts;
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using Microsoft.CodeAnalysis.CodeFixes;
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using Microsoft.CodeAnalysis.Diagnostics;
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using NUnit.Analyzers.Constants;
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using NUnit.Analyzers.UseSpecificConstraint;
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using NUnit.Framework;
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namespace NUnit.Analyzers.Tests.UseSpecificConstraint
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{
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public class UseSpecificConstraintCodeFixTests
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{
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private static readonly DiagnosticAnalyzer analyzer = new UseSpecificConstraintAnalyzer();
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private static readonly CodeFixProvider fix = new UseSpecificConstraintCodeFix();
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private static readonly ExpectedDiagnostic expectedDiagnostic =
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ExpectedDiagnostic.Create(AnalyzerIdentifiers.UseSpecificConstraint);
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private static readonly string[][] EqualToSpecificConstraint =
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[
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["false", "False"],
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#if NUNIT4
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["default(bool)", "Default"],
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#else
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["default(bool)", "False"],
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#endif
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["true", "True"],
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["null", "Null"],
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["default(object)", "Null"],
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["default(string)", "Null"],
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#if NUNIT4
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["default(int)", "Default"],
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#endif
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];
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[TestCaseSource(nameof(EqualToSpecificConstraint))]
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public void AnalyzeForSpecificConstraint(string literal, string constraint) => AnalyzeForEqualTo(literal, constraint);
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#if NUNIT4
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[Test]
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public void AnalyzeForIsDefault() => AnalyzeForEqualTo("default", "Default",
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Settings.Default.WithAllowedCompilerDiagnostics(AllowedCompilerDiagnostics.WarningsAndErrors));
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#endif
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private static void AnalyzeForEqualTo(string literal, string constraint, Settings? settings = null)
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{
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AnalyzeForEqualTo("Is", string.Empty, literal, constraint, settings);
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AnalyzeForEqualTo("Is", ".And.Not.Empty", literal, constraint, settings);
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AnalyzeForEqualTo("Is.Not", string.Empty, literal, constraint, settings);
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AnalyzeForEqualTo("Is.EqualTo(0).Or", string.Empty, literal, constraint, settings);
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}
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private static void AnalyzeForEqualTo(string prefix, string suffix, string literal, string constraint, Settings? settings = null)
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{
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var testCode = TestUtility.WrapInTestMethod(
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$"Assert.That(false, ↓{prefix}.EqualTo({literal}){suffix});");
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var fixedCode = TestUtility.WrapInTestMethod(
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$"Assert.That(false, {prefix}.{constraint}{suffix});");
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RoslynAssert.CodeFix(analyzer, fix,
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expectedDiagnostic.WithMessage($"Replace 'Is.EqualTo({literal})' with 'Is.{constraint}' constraint"),
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testCode, fixedCode,
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settings: settings);
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}
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}
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}

‎src/nunit.analyzers/Constants/AnalyzerIdentifiers.cs‎

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#region Style
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internal const string SimplifyValues = "NUnit4001";
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internal const string UseSpecificConstraint = "NUnit4002";
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#endregion
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}

‎src/nunit.analyzers/Constants/AnalyzerPropertyKeys.cs‎

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internal const string MinimumNumberOfArguments = nameof(AnalyzerPropertyKeys.MinimumNumberOfArguments);
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internal const string SupportsEnterMultipleScope = nameof(AnalyzerPropertyKeys.SupportsEnterMultipleScope);
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internal const string SpecificConstraint = nameof(AnalyzerPropertyKeys.SpecificConstraint);
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}
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}

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