feat: add assertion for NotExist (#50)

Add assertions for `IFileInfo` and `IDirectoryInfo` to `NotExist`, which
checks, that the `Exists` flag is `false`.

Author: vbreuss

Source/Testably.Abstractions.FluentAssertions/FileSystemInfoAssertions.cs

@@ -36,4 +36,25 @@ public AndConstraint<TFileSystemInfo> Exist(
 
 		return new AndConstraint<TFileSystemInfo>(Subject!);
 	}
+
+	/// <summary>
+	///     Asserts that the current file or directory does not exist.
+	/// </summary>
+	public AndConstraint<TFileSystemInfo> NotExist(
+		string because = "", params object[] becauseArgs)
+	{
+		Execute.Assertion
+			.WithDefaultIdentifier(Identifier)
+			.BecauseOf(because, becauseArgs)
+			.ForCondition(Subject != null)
+			.FailWith("You can't assert that the {context} does not exist if it is null.")
+			.Then
+			.Given(() => Subject!)
+			.ForCondition(fileSystemInfo => !fileSystemInfo.Exists)
+			.FailWith(
+				"Expected {context} {0} not to exist{reason}, but it did.",
+				fileSystemInfo => fileSystemInfo.Name);
+
+		return new AndConstraint<TFileSystemInfo>(Subject!);
+	}
 }

Tests/Testably.Abstractions.FluentAssertions.Tests/FileSystemInfoAssertionsTests.cs

@@ -27,7 +27,7 @@ public void Exist_ForDirectoryInfo_Null_ShouldThrow(string because)
 
 	[Theory]
 	[AutoData]
-	public void Exist_ForDirectoryInfo_WithCorrectDirectory_ShouldNotThrow(string directoryName)
+	public void Exist_ForDirectoryInfo_WithExistingDirectory_ShouldNotThrow(string directoryName)
 	{
 		MockFileSystem fileSystem = new();
 		fileSystem.Initialize()
@@ -40,7 +40,7 @@ public void Exist_ForDirectoryInfo_WithCorrectDirectory_ShouldNotThrow(string di
 
 	[Theory]
 	[AutoData]
-	public void Exist_ForDirectoryInfo_WithoutCorrectDirectory_ShouldThrow(
+	public void Exist_ForDirectoryInfo_WithoutExistingDirectory_ShouldThrow(
 		string directoryName,
 		string because)
 	{
@@ -97,7 +97,7 @@ public void Exist_ForFileInfo_Null_ShouldThrow(string because)
 
 	[Theory]
 	[AutoData]
-	public void Exist_ForFileInfo_WithCorrectFile_ShouldNotThrow(string fileName)
+	public void Exist_ForFileInfo_WithExistingFile_ShouldNotThrow(string fileName)
 	{
 		MockFileSystem fileSystem = new();
 		fileSystem.Initialize()
@@ -110,7 +110,7 @@ public void Exist_ForFileInfo_WithCorrectFile_ShouldNotThrow(string fileName)
 
 	[Theory]
 	[AutoData]
-	public void Exist_ForFileInfo_WithoutCorrectFile_ShouldThrow(
+	public void Exist_ForFileInfo_WithoutExistingFile_ShouldThrow(
 		string fileName,
 		string because)
 	{
@@ -148,4 +148,131 @@ public void Exist_ForFileInfo_WithSameDirectory_ShouldThrow(
 		exception!.Message.Should()
 			.Be($"Expected file \"{fileName}\" to exist {because}, but it did not.");
 	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForDirectoryInfo_Null_ShouldThrow(string because)
+	{
+		IDirectoryInfo? sut = null;
+
+		Exception? exception = Record.Exception(() =>
+		{
+			sut.Should().NotExist(because);
+		});
+
+		exception.Should().NotBeNull();
+		exception!.Message.Should().Contain("null");
+		exception.Message.Should().NotContain(because);
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForDirectoryInfo_WithExistingDirectory_ShouldThrow(
+		string directoryName,
+		string because)
+	{
+		MockFileSystem fileSystem = new();
+		fileSystem.Initialize()
+			.WithSubdirectories(directoryName);
+
+		IDirectoryInfo sut = fileSystem.DirectoryInfo.New(directoryName);
+
+		Exception? exception = Record.Exception(() =>
+		{
+			sut.Should().NotExist(because);
+		});
+
+		exception.Should().NotBeNull();
+		exception!.Message.Should()
+			.Be($"Expected directory \"{directoryName}\" not to exist {because}, but it did.");
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForDirectoryInfo_WithoutExistingDirectory_ShouldNotThrow(
+		string directoryName)
+	{
+		MockFileSystem fileSystem = new();
+		fileSystem.Initialize();
+		IDirectoryInfo sut = fileSystem.DirectoryInfo.New(directoryName);
+
+		sut.Should().NotExist();
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForDirectoryInfo_WithSameFile_ShouldNotThrow(
+		string fileName,
+		string because)
+	{
+		MockFileSystem fileSystem = new();
+		fileSystem.Initialize();
+		fileSystem.File.WriteAllText(fileName, "some content");
+		IDirectoryInfo sut = fileSystem.DirectoryInfo.New(fileName);
+
+		sut.Should().NotExist(because);
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForFileInfo_Null_ShouldThrow(string because)
+	{
+		IFileInfo? sut = null;
+
+		Exception? exception = Record.Exception(() =>
+		{
+			sut.Should().NotExist(because);
+		});
+
+		exception.Should().NotBeNull();
+		exception!.Message.Should().Contain("null");
+		exception.Message.Should().NotContain(because);
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForFileInfo_WithExistingFile_ShouldThrow(
+		string fileName,
+		string because)
+	{
+		MockFileSystem fileSystem = new();
+		fileSystem.Initialize()
+			.WithFile(fileName);
+		IFileInfo sut = fileSystem.FileInfo.New(fileName);
+
+		Exception? exception = Record.Exception(() =>
+		{
+			sut.Should().NotExist(because);
+		});
+
+		exception.Should().NotBeNull();
+		exception!.Message.Should()
+			.Be($"Expected file \"{fileName}\" not to exist {because}, but it did.");
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForFileInfo_WithoutExistingFile_ShouldNotThrow(string fileName)
+	{
+		MockFileSystem fileSystem = new();
+		fileSystem.Initialize();
+
+		IFileInfo sut = fileSystem.FileInfo.New(fileName);
+
+		sut.Should().NotExist();
+	}
+
+	[Theory]
+	[AutoData]
+	public void NotExist_ForFileInfo_WithSameDirectory_ShouldNotThrow(
+		string fileName,
+		string because)
+	{
+		MockFileSystem fileSystem = new();
+		fileSystem.Initialize();
+		fileSystem.Directory.CreateDirectory(fileName);
+		IFileInfo sut = fileSystem.FileInfo.New(fileName);
+
+		sut.Should().NotExist(because);
+	}
 }