Constraints

This page lists all the constraints available in NUnit.

For additional topics, see:

Alphabetical List of Constraints

Constraint Name Example
AllItemsConstraint Assert.That(numbers, Is.All.GreaterThan(0));
AndConstraint Assert.That(value, Is.GreaterThan(0).And.LessThan(100));
AnyOfConstraint Assert.That(42, Is.AnyOf(0, -1, 42, 100));
AssignableFromConstraint Assert.That("Hello", Is.AssignableFrom<string>());
AssignableToConstraint Assert.That("Hello", Is.AssignableTo<object>());
AttributeConstraint Assert.That(typeof(MyFixture), Has.Attribute<CategoryAttribute>().Property("Name").EqualTo("Database"));
AttributeExistsConstraint Assert.That(typeof(MyClass), Has.Attribute<SerializableAttribute>());
BinarySerializableConstraint Assert.That(someObject, Is.BinarySerializable);
CollectionEquivalentConstraint Assert.That(new[] { 3, 2, 1 }, Is.EquivalentTo(new[] { 1, 2, 3 }));
CollectionOrderedConstraint Assert.That(new[] { 1, 2, 3 }, Is.Ordered);
CollectionSubsetConstraint Assert.That(new[] { 1, 3 }, Is.SubsetOf(new[] { 1, 2, 3 }));
CollectionSupersetConstraint Assert.That(new[] { 1, 2, 3 }, Is.SupersetOf(new[] { 1, 3 }));
ContainsConstraint Assert.That("Hello World", Does.Contain("World"));
DefaultConstraint Assert.That(default(DateTime), Is.Default);
DelayedConstraint Assert.That(() => flag, Is.True.After(500).MilliSeconds.PollEvery(50).MilliSeconds);
DictionaryContainsKeyConstraint Assert.That(dictionary, Does.ContainKey("Alice"));
DictionaryContainsKeyValuePairConstraint Assert.That(dictionary, Does.ContainKey("Hello").WithValue("World"));
DictionaryContainsValueConstraint Assert.That(dictionary, Does.ContainValue(85));
EmptyCollectionConstraint Assert.That(new List<string>(), Is.Empty);
EmptyConstraint Assert.That(value, Is.Empty);
EmptyDirectoryConstraint Assert.That(new DirectoryInfo(path), Is.Empty);
EmptyStringConstraint Assert.That("", Is.Empty);
EndsWithConstraint Assert.That("Hello World!", Does.EndWith("World!"));
EqualConstraint Assert.That(2 + 2, Is.EqualTo(4));
ExactCountConstraint Assert.That(numbers, Has.Exactly(2).GreaterThan(3));
ExactTypeConstraint Assert.That("Hello", Is.TypeOf<string>());
FalseConstraint Assert.That(2 + 2 == 5, Is.False);
FileOrDirectoryExistsConstraint Assert.That(new FileInfo(path), Does.Exist);
GreaterThanConstraint Assert.That(7, Is.GreaterThan(3));
GreaterThanOrEqualConstraint Assert.That(7, Is.GreaterThanOrEqualTo(7));
InstanceOfTypeConstraint Assert.That("Hello", Is.InstanceOf<object>());
LessThanConstraint Assert.That(3, Is.LessThan(7));
LessThanOrEqualConstraint Assert.That(3, Is.LessThanOrEqualTo(7));
MultipleOfConstraint Assert.That(12, Is.MultipleOf(3));
NaNConstraint Assert.That(0.0 / 0.0, Is.NaN);
NoItemConstraint Assert.That(numbers, Has.None.LessThan(0));
NotConstraint Assert.That(42, Is.Not.EqualTo(0));
NullConstraint Assert.That(obj, Is.Null);
OrConstraint Assert.That(value, Is.LessThan(10).Or.GreaterThan(40));
PropertyConstraint Assert.That(person, Has.Property("Age").GreaterThan(18));
PropertyExistsConstraint Assert.That("Hello", Has.Property("Length"));
RangeConstraint Assert.That(5, Is.InRange(1, 10));
RegexConstraint Assert.That("555-123-4567", Does.Match(@"^\d{3}-\d{3}-\d{4}$"));
ReusableConstraint ReusableConstraint myConstraint = Is.Not.Null;
SameAsConstraint Assert.That(obj2, Is.SameAs(obj1));
SamePathConstraint Assert.That("/folder1/./junk/../folder2", Is.SamePath("/folder1/folder2"));
SamePathOrUnderConstraint Assert.That("/folder1/folder2/folder3", Is.SamePathOrUnder("/folder1/folder2"));
SomeItemsConstraint Assert.That(numbers, Has.Some.GreaterThan(3));
StartsWithConstraint Assert.That("Hello World!", Does.StartWith("Hello"));
SubPathConstraint Assert.That("/folder1/folder2", Is.SubPathOf("/folder1/"));
SubstringConstraint Assert.That("Hello World!", Does.Contain("lo Wor"));
ThrowsConstraint Assert.That(() => int.Parse("abc"), Throws.TypeOf<FormatException>());
ThrowsNothingConstraint Assert.That(() => Add(1, 2), Throws.Nothing);
TrueConstraint Assert.That(2 + 2 == 4, Is.True);
UniqueItemsConstraint Assert.That(new[] { 1, 2, 3 }, Is.Unique);
WhiteSpaceConstraint Assert.That(" ", Is.WhiteSpace);
XmlSerializableConstraint Assert.That(someObject, Is.XmlSerializable);

Constraints by Category

Collection Constraints

Constraint Name Example
AllItemsConstraint Assert.That(numbers, Is.All.GreaterThan(0));
AnyOfConstraint Assert.That(42, Is.AnyOf(0, -1, 42, 100));
CollectionEquivalentConstraint Assert.That(new[] { 3, 2, 1 }, Is.EquivalentTo(new[] { 1, 2, 3 }));
CollectionOrderedConstraint Assert.That(new[] { 1, 2, 3 }, Is.Ordered);
CollectionSubsetConstraint Assert.That(new[] { 1, 3 }, Is.SubsetOf(new[] { 1, 2, 3 }));
CollectionSupersetConstraint Assert.That(new[] { 1, 2, 3 }, Is.SupersetOf(new[] { 1, 3 }));
DictionaryContainsKeyConstraint Assert.That(dictionary, Does.ContainKey("Alice"));
DictionaryContainsKeyValuePairConstraint Assert.That(dictionary, Does.ContainKey("Hello").WithValue("World"));
DictionaryContainsValueConstraint Assert.That(dictionary, Does.ContainValue(85));
EmptyCollectionConstraint Assert.That(new List<string>(), Is.Empty);
ExactCountConstraint Assert.That(numbers, Has.Exactly(2).GreaterThan(3));
NoItemConstraint Assert.That(numbers, Has.None.LessThan(0));
SomeItemsConstraint Assert.That(numbers, Has.Some.GreaterThan(3));
UniqueItemsConstraint Assert.That(new[] { 1, 2, 3 }, Is.Unique);

Comparison Constraints

Constraint Name Example
GreaterThanConstraint Assert.That(7, Is.GreaterThan(3));
GreaterThanOrEqualConstraint Assert.That(7, Is.GreaterThanOrEqualTo(7));
LessThanConstraint Assert.That(3, Is.LessThan(7));
LessThanOrEqualConstraint Assert.That(3, Is.LessThanOrEqualTo(7));
MultipleOfConstraint Assert.That(12, Is.MultipleOf(3));
RangeConstraint Assert.That(5, Is.InRange(1, 10));

Compound Constraints

Constraint Name Example
AndConstraint Assert.That(value, Is.GreaterThan(0).And.LessThan(100));
NotConstraint Assert.That(42, Is.Not.EqualTo(0));
OrConstraint Assert.That(value, Is.LessThan(10).Or.GreaterThan(40));

Condition Constraints

Constraint Name Example
DefaultConstraint Assert.That(default(DateTime), Is.Default);
EmptyConstraint Assert.That(value, Is.Empty);
FalseConstraint Assert.That(2 + 2 == 5, Is.False);
NaNConstraint Assert.That(0.0 / 0.0, Is.NaN);
NullConstraint Assert.That(obj, Is.Null);
TrueConstraint Assert.That(2 + 2 == 4, Is.True);
WhiteSpaceConstraint Assert.That(" ", Is.WhiteSpace);

File and Directory Constraints

Constraint Name Example
EmptyDirectoryConstraint Assert.That(new DirectoryInfo(path), Is.Empty);
FileOrDirectoryExistsConstraint Assert.That(new FileInfo(path), Does.Exist);
SamePathConstraint Assert.That("/folder1/./junk/../folder2", Is.SamePath("/folder1/folder2"));
SamePathOrUnderConstraint Assert.That("/folder1/folder2/folder3", Is.SamePathOrUnder("/folder1/folder2"));
SubPathConstraint Assert.That("/folder1/folder2", Is.SubPathOf("/folder1/"));

String Constraints

Constraint Name Example
ContainsConstraint Assert.That("Hello World", Does.Contain("World"));
EmptyStringConstraint Assert.That("", Is.Empty);
EndsWithConstraint Assert.That("Hello World!", Does.EndWith("World!"));
RegexConstraint Assert.That("555-123-4567", Does.Match(@"^\d{3}-\d{3}-\d{4}$"));
StartsWithConstraint Assert.That("Hello World!", Does.StartWith("Hello"));
SubstringConstraint Assert.That("Hello World!", Does.Contain("lo Wor"));

Type Constraints

Constraint Name Example
AssignableFromConstraint Assert.That("Hello", Is.AssignableFrom<string>());
AssignableToConstraint Assert.That("Hello", Is.AssignableTo<object>());
ExactTypeConstraint Assert.That("Hello", Is.TypeOf<string>());
InstanceOfTypeConstraint Assert.That("Hello", Is.InstanceOf<object>());

See also