#3053: Class data derived from TheoryData<SomeType[]> is broken

Author: bradwilson

src/xunit.core/ClassDataAttribute.cs

@@ -31,19 +31,21 @@ public ClassDataAttribute(Type @class)
         /// <inheritdoc/>
         public override IEnumerable<object[]> GetData(MethodInfo testMethod)
         {
-            IEnumerable<object[]> data = Activator.CreateInstance(Class) as IEnumerable<object[]>;
-            if (data == null)
-                throw new ArgumentException(
-                    string.Format(
-                        CultureInfo.CurrentCulture,
-                        "{0} must implement IEnumerable<object[]> to be used as ClassData for the test method named '{1}' on {2}",
-                        Class.FullName,
-                        testMethod.Name,
-                        testMethod.DeclaringType.FullName
-                    )
-                );
+            var dataObj = Activator.CreateInstance(Class);
+            if (dataObj is ITheoryData theoryData)
+                return theoryData.GetData();
+            if (dataObj is IEnumerable<object[]> enumerable)
+                return enumerable;
 
-            return data;
+            throw new ArgumentException(
+                string.Format(
+                    CultureInfo.CurrentCulture,
+                    "{0} must implement IEnumerable<object[]> to be used as ClassData for the test method named '{1}' on {2}",
+                    Class.FullName,
+                    testMethod.Name,
+                    testMethod.DeclaringType.FullName
+                )
+            );
         }
     }
 }

test/test.xunit.execution/Acceptance/Xunit2TheoryAcceptanceTests.cs

@@ -677,6 +677,41 @@ public IEnumerator<object[]> GetEnumerator()
             IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
         }
 
+        [Fact]
+        public void ClassDataFromArray()
+        {
+            var testMessages = Run<ITestResultMessage>(typeof(ClassWithArrayData));
+
+            Assert.Collection(
+                testMessages.OfType<ITestPassed>().Select(p => p.Test.DisplayName).OrderBy(x => x),
+                name => Assert.Equal("Xunit2TheoryAcceptanceTests+ClassDataTests+ClassWithArrayData.ExampleParameterizedTestMethod(values: [\"0\", \"2\", \"4\"])", name),
+                name => Assert.Equal("Xunit2TheoryAcceptanceTests+ClassDataTests+ClassWithArrayData.ExampleParameterizedTestMethod(values: [\"0\", \"2\"])", name),
+                name => Assert.Equal("Xunit2TheoryAcceptanceTests+ClassDataTests+ClassWithArrayData.ExampleParameterizedTestMethod(values: [\"0\"])", name)
+            );
+            Assert.Empty(testMessages.OfType<ITestFailed>());
+            Assert.Empty(testMessages.OfType<ITestSkipped>());
+        }
+
+        class ClassWithArrayData
+        {
+            [Theory]
+            [ClassData(typeof(ClassDataFromArrayDataSource))]
+            public void ExampleParameterizedTestMethod(string[] values)
+            {
+                Assert.All(values, s => Assert.True(s.Length < 10));
+            }
+        }
+
+        class ClassDataFromArrayDataSource : TheoryData<string[]>
+        {
+            public ClassDataFromArrayDataSource()
+            {
+                Add(["0"]);
+                Add(["0", "2"]);
+                Add(["0", "2", "4"]);
+            }
+        }
+
         [Fact]
         public void NoDefaultConstructor_Fails()
         {