xunit: define codefixes for StringAsserts

[Meir017]

The asserts defined in https://github.com/xunit/assert.xunit/blob/main/StringAsserts.cs

• Contains(string expectedSubstring, string actualString) add support for xunit StringAsserts Contains #221
• DoesNotContain(string expectedSubstring, string actualString) add support for xunit StringAsserts DoesNotContain #223
• DoesNotMatch(string expectedRegexPattern, string actualString) add support for xunit StringAsserts DoesNotMatches #225
• DoesNotMatch(Regex expectedRegex, string actualString) add support for xunit StringAsserts DoesNotMatches #225
• Matches(string expectedRegexPattern, string actualString) add support for xunit StringAsserts Matches #224
• Matches(Regex expectedRegex, string actualString) add support for xunit StringAsserts Matches #224
• Empty(string value) add support for xunit StringAsserts Empty #226
• EndsWith(string expectedEndString, string actualString) add support for xunit StringAsserts EndsWith #227
• StartsWith(string expectedStartString, string actualString) add support for xunit StringAsserts StartsWith #228
• Equal(string expected, string actual) add support for xunit StringAsserts Equals #229

[Meir017]

@jnyrup / @dennisdoomen any idea about an equivalent for using StringComparison in fluentassertions? it's not exposed anywhere as an argument.

From what I was able to tell there are the following:

for Assert.Equal:

• .Should().Be for StringComparison.Ordinal
• .Should().BeEquivalentTo for StringComparison.OrdinalIgnoreCase

for Assert.Contains:

• .Should().Contain for StringComparison.Ordinal
• .Should().ContainEquivalentOf for StringComparison.OrdinalIgnoreCase

for Assert.NotContains:

• .Should().NotContain for StringComparison.Ordinal
• .Should().NotContainEquivalentOf for StringComparison.OrdinalIgnoreCase

for Assert.EndsWith:

• .Should().EndWith for StringComparison.Ordinal
• .Should().EndWithEquivalentOf for StringComparison.OrdinalIgnoreCase

for Assert.StartsWith:

• .Should().StartWith for StringComparison.Ordinal
• .Should().StartWithEquivalentOf for StringComparison.OrdinalIgnoreCase

so for constant values of using explicitly StringComparison.Ordinal and StringComparison.OrdinalIgnoreCase we should be able to hint at the correct usage.

What about

• StringComparison.CurrentCulture
• StringComparison.CurrentCultureIgnoreCase
• StringComparison.InvariantCulture
• StringComparison.InvariantCultureIgnoreCase

should each of these suggest to use StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase?

[jnyrup]

There's no idiomatic way to pass a StringComparison to the string assertions.

There are ugly ways

"someString".Should().Match(e => string.Equals(e, "SoMeStRiNg", StringComparison.OrdinalIgnoreCase));
"someString".As<object>().Should().Be("SoMeStRiNg", StringComparer.OrdinalIgnoreCase);

Note that in v6 the Equivalent APIs besides casing also ignore leading and trailing whitespace.

For v7 we're currently having discussing on how to improve on this
fluentassertions/fluentassertions#2339
fluentassertions/fluentassertions#2364