Merge pull request #1072 from nunit/defaultConstraint

Defaultconstraint

Author: OsirisTerje

docs/articles/nunit/writing-tests/constraints/DefaultConstraint.md

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+# DefaultConstraint
+
+`DefaultConstraint` tests that the actual value is the default value for the type.
+
+It is implemented equal to the C# keyword `default`.
+
+## Constructor
+
+```csharp
+DefaultConstraint()
+```
+
+## Syntax
+
+```csharp
+Is.Default
+Has.Length.Default
+Has.Count.Default
+Is.Not.Default
+```
+
+All resolvable properties of `Has` can be used with the `Default` property.
+`Default` can be used with the `Not` operator.
+`Default` can be used with the combinatorial operators.
+
+## Examples of use
+
+[!code-csharp[DefaultConstraintExample](~/snippets/Snippets.NUnit/DefaultConstraintExamples.cs#DefaultConstraintExample)]
+
+## Version
+
+From version 4.0.0

docs/snippets/Snippets.NUnit/DefaultConstraintExamples.cs

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+using NUnit.Framework;
+
+namespace Snippets.NUnit;
+
+public class DefaultConstraintExamples
+{
+    #region DefaultConstraintExample
+    [Test]
+    public void DefaultConstraintExample()
+    {
+        string defaultLength = string.Empty;
+        var nonDefaultLength = "1";
+        var defaultList = new List<int>(); 
+        var nonDefaultList = new List<int> {1};
+        var defaultDate = default(DateTime);
+        var nonDefaultDate = DateTime.Now;
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(defaultLength.Length, Is.Zero);
+            Assert.That(defaultLength.Length, Is.Default);
+            Assert.That(defaultLength, Has.Length.Default);
+            Assert.That(defaultLength, Has.Property("Length").Default);
+            Assert.That(defaultList, Has.Count.Default);
+            Assert.That(defaultDate, Is.Default);
+
+            Assert.That(nonDefaultLength.Length, Is.Not.Zero);
+            Assert.That(nonDefaultLength.Length, Is.Not.Default);
+            Assert.That(nonDefaultLength, Has.Length.Not.Default);
+            Assert.That(nonDefaultLength, Has.Property("Length").Not.Default);
+            Assert.That(nonDefaultList, Has.Count.Not.Default);
+            Assert.That(nonDefaultDate, Is.Not.Default);
+        }
+    }
+    #endregion
+}