Add C# tests.

src/Compilers/CSharp/Test/Symbol/Compilation/CompilationAPITests.cs

@@ -2150,6 +2150,52 @@ public void PreviousSubmissionWithError()
             Assert.Throws<InvalidOperationException>(() => CreateSubmission("a + 1", previous: s0));
         }
 
+        [Fact()]
+        public void CreateAnonymousType_IncorrectLengths()
+        {
+            var compilation = CSharpCompilation.Create("HelloWorld");
+            Assert.Throws<ArgumentException>(() =>
+                compilation.CreateAnonymousTypeSymbol(
+                    ImmutableArray.Create((ITypeSymbol)null),
+                    ImmutableArray.Create("m1", "m2")));
+        }
+
+        [Fact()]
+        public void CreateAnonymousType_NothingArgument()
+        {
+            var compilation = CSharpCompilation.Create("HelloWorld");
+            Assert.Throws<ArgumentNullException>(() =>
+                compilation.CreateAnonymousTypeSymbol(
+                        ImmutableArray.Create((ITypeSymbol)null),
+                        ImmutableArray.Create("m1")));
+        }
+
+        [Fact()]
+        public void CreateAnonymousType1()
+        {
+            var compilation = CSharpCompilation.Create("HelloWorld");
+            var type = compilation.CreateAnonymousTypeSymbol(
+                        ImmutableArray.Create<ITypeSymbol>(compilation.GetSpecialType(SpecialType.System_Int32)),
+                        ImmutableArray.Create("m1"));
+
+            Assert.True(type.IsAnonymousType);
+            Assert.Equal(1, type.GetMembers().OfType<IPropertySymbol>().Count());
+            Assert.Equal("<anonymous type: int m1>", type.ToDisplayString());
+        }
+
+        [Fact()]
+        public void CreateAnonymousType2()
+        {
+            var compilation = CSharpCompilation.Create("HelloWorld");
+            var type = compilation.CreateAnonymousTypeSymbol(
+                        ImmutableArray.Create<ITypeSymbol>(compilation.GetSpecialType(SpecialType.System_Int32), compilation.GetSpecialType(SpecialType.System_Boolean)),
+                        ImmutableArray.Create("m1", "m2"));
+
+            Assert.True(type.IsAnonymousType);
+            Assert.Equal(2, type.GetMembers().OfType<IPropertySymbol>().Count());
+            Assert.Equal("<anonymous type: int m1, bool m2>", type.ToDisplayString());
+        }
+
         #region Script return values
 
         [Fact]