test: add test helper

Testing/CASLTests/Helpers/TestHelpers.cs

@@ -1,4 +1,4 @@
-// <copyright file="TestHelpers.cs" company="KinsonDigital">
+// <copyright file="TestHelpers.cs" company="KinsonDigital">
 // Copyright (c) KinsonDigital. All rights reserved.
 // </copyright>
 
@@ -215,6 +215,30 @@ public static void SetFieldToNull(this object fieldContainer, string fieldName)
         foundField.SetValue(fieldContainer, null);
     }
 
+    /// <summary>
+    /// Sets a field with a name that matches the given <paramref name="fieldName"/> to the value of null.
+    /// </summary>
+    /// <param name="fieldContainer">The object that contains the field.</param>
+    /// <param name="fieldName">The name of the field.</param>
+    /// <param name="value">The value to set the field to.</param>
+    /// <typeparam name="T">The type of parameter.</typeparam>
+    public static void SetFieldValue<T>(this object fieldContainer, string fieldName, T value)
+    {
+        fieldContainer.Should().NotBeNull("setting the field value of a null object is not possible.");
+        fieldName.Should().NotBeNullOrEmpty("setting an field value requires a non-empty or null field name.");
+
+        var fields = fieldContainer.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance);
+
+        fields.Should().HaveCountGreaterThan(0, $"no fields exist in the object.");
+
+        var foundField = Array.Find(fields, f => f.Name == fieldName);
+
+        foundField.Should().NotBeNull($"a field with the name '{fieldName}' does not exist in the object.");
+        foundField.FieldType.Should().Be(typeof(T), "the generic type should match the actual field type.");
+
+        foundField.SetValue(fieldContainer, value);
+    }
+
     /// <summary>
     /// Gets the boolean field value with a name that matches the given <paramref name="fieldName"/> inside of the object
     /// <paramref name="fieldContainer"/>.