Substring Constraint

SubstringConstraint tests that a string contains the expected substring.

Usage

Does.Contain(string expected)
Does.Not.Contain(string expected)

Modifiers

.IgnoreCase
.Using(StringComparison comparisonType)
.Using(CultureInfo culture)

Examples

[Test]
public void SubstringConstraint_Examples()
{
    string phrase = "Make your tests fail before passing!";

    Assert.That(phrase, Does.Contain("tests"));
    Assert.That(phrase, Does.Contain("TESTS").IgnoreCase);
    Assert.That(phrase, Does.Not.Contain("missing"));
}

Specifying a StringComparison

[Test]
public void SubstringConstraint_StringComparison_Examples()
{
    // IgnoreCase modifier
    Assert.That("Hello World!", Does.Contain("WORLD").IgnoreCase);
    Assert.That("Hello World!", Does.Contain("World"));
}

Specifying a CultureInfo

The Using(CultureInfo) modifier allows for culture-specific string comparisons. It can be combined with .IgnoreCase for case-insensitive culture-aware comparisons:

// Using Turkish culture where 'i' and 'I' have special casing rules
Assert.That("Hello TITLE World", Does.Contain("title").IgnoreCase.Using(new CultureInfo("tr-TR")));

// Culture-specific comparison without case-insensitivity
Assert.That("Straße Street", Does.Contain("Straße").Using(new CultureInfo("de-DE")));

Notes

  1. Only one Using modifier may be specified. Attempting to use multiple Using modifiers will throw an InvalidOperationException.
  2. When using Does.Contain() with a non-string actual value, it tests for collection membership instead. See ContainsConstraint for details.

See Also