diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
index 156c4b0d58bb247253214fb9b8661bcc0bb71590..aed887a91dcd6294b61cf31b32e5ba540b3bef3f 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
@@ -59283,7 +59283,7 @@ static void Main()
                 });
         }
 
-        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/30747 Type load failed.")]
+        [Fact]
         [WorkItem(30747, "https://github.com/dotnet/roslyn/issues/30747")]
         public void MissingTypeKindBasisTypes()
         {
@@ -59316,7 +59316,9 @@ interface I2
             var compilation2 = CreateEmptyCompilation(source2, options: WithNonNullTypesTrue(TestOptions.ReleaseDll), references: new[] { compilation1.EmitToImageReference(), MinCorlibRef });
 
             compilation2.VerifyEmitDiagnostics();
-            CompileAndVerify(compilation2);
+
+            // Verification against a corlib not named exactly mscorlib is expected to fail.
+            CompileAndVerify(compilation2, verify: Verification.Fails);
 
             Assert.Equal(TypeKind.Struct, compilation2.GetTypeByMetadataName("A").TypeKind);
             Assert.Equal(TypeKind.Enum, compilation2.GetTypeByMetadataName("B").TypeKind);
@@ -59327,7 +59329,7 @@ interface I2
             var compilation3 = CreateEmptyCompilation(source2, options: WithNonNullTypesTrue(TestOptions.ReleaseDll), references: new[] { compilation1.ToMetadataReference(), MinCorlibRef });
 
             compilation3.VerifyEmitDiagnostics();
-            CompileAndVerify(compilation3);
+            CompileAndVerify(compilation3, verify: Verification.Fails);
 
             Assert.Equal(TypeKind.Struct, compilation3.GetTypeByMetadataName("A").TypeKind);
             Assert.Equal(TypeKind.Enum, compilation3.GetTypeByMetadataName("B").TypeKind);
@@ -59369,15 +59371,13 @@ interface I2
 
             compilation5.VerifyEmitDiagnostics(
                 // warning CS8021: No value for RuntimeMetadataVersion found. No assembly containing System.Object was found nor was a value for RuntimeMetadataVersion specified through options.
-                Diagnostic(ErrorCode.WRN_NoRuntimeMetadataVersion).WithLocation(1, 1)
-                );
-            CompileAndVerify(compilation5);
-
-            Assert.Equal(TypeKind.Struct, compilation5.GetTypeByMetadataName("A").TypeKind);
-            Assert.Equal(TypeKind.Enum, compilation5.GetTypeByMetadataName("B").TypeKind);
-            Assert.Equal(TypeKind.Class, compilation5.GetTypeByMetadataName("C").TypeKind);
-            Assert.Equal(TypeKind.Delegate, compilation5.GetTypeByMetadataName("D").TypeKind);
-            Assert.Equal(TypeKind.Interface, compilation5.GetTypeByMetadataName("I1").TypeKind);
+                Diagnostic(ErrorCode.WRN_NoRuntimeMetadataVersion).WithLocation(1, 1),
+                // error CS0518: Predefined type 'System.Attribute' is not defined or imported
+                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound).WithArguments("System.Attribute").WithLocation(1, 1),
+                // error CS0518: Predefined type 'System.Attribute' is not defined or imported
+                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound).WithArguments("System.Attribute").WithLocation(1, 1),
+                // error CS0518: Predefined type 'System.Byte' is not defined or imported
+                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound).WithArguments("System.Byte").WithLocation(1, 1));
 
             var compilation6 = CreateEmptyCompilation(source2, options: WithNonNullTypesTrue(TestOptions.ReleaseDll), references: new[] { compilation1.EmitToImageReference(), MscorlibRef });
 
diff --git a/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs b/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs
index 5eb499b4e662b59dd108366ea591070b969cdf77..dfff3a63af5983c34f99f68e31f3139ff80e0fa8 100644
--- a/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs
+++ b/src/Compilers/Test/Utilities/CSharp/CSharpTestBase.cs
@@ -2032,6 +2032,33 @@ protected static CSharpCompilation CreateCompilationWithIndexAndRangeAndSpan(CSh
         }
         #endregion
 
+        #region Theory Helpers
+
+        public static IEnumerable<object[]> NonNullTypesTrueAndFalseDebugDll
+        {
+            get
+            {
+                return new List<object[]>()
+                {
+                    new object[] { WithNonNullTypesTrue(TestOptions.DebugDll) },
+                    new object[] { WithNonNullTypesFalse(TestOptions.DebugDll) }
+                };
+            }
+        }
+
+        public static IEnumerable<object[]> NonNullTypesTrueAndFalseReleaseDll
+        {
+            get
+            {
+                return new List<object[]>()
+                {
+                    new object[] { WithNonNullTypesTrue(TestOptions.ReleaseDll) },
+                    new object[] { WithNonNullTypesFalse(TestOptions.ReleaseDll) }
+                };
+            }
+        }
+        #endregion
+
         protected static readonly string s_IAsyncEnumerable = @"
 namespace System.Collections.Generic
 {
diff --git a/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ExpressionCompilerTests.cs b/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ExpressionCompilerTests.cs
index aa92b7c4f9b8048c71c1c5c8e9aceae967566647..d629c8203eac68e45d922023cde5335d1e993ee9 100644
--- a/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ExpressionCompilerTests.cs
+++ b/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ExpressionCompilerTests.cs
@@ -3029,8 +3029,9 @@ .maxstack  1
             });
         }
 
-        [Fact]
-        public void EvaluateCapturedLocalsOutsideLambda()
+        [Theory]
+        [MemberData(nameof(NonNullTypesTrueAndFalseDebugDll))]
+        public void EvaluateCapturedLocalsOutsideLambda(CSharpCompilationOptions options)
         {
             var source =
 @"class A
@@ -3067,7 +3068,7 @@ void M<T>(object x) where T : A, new()
         }
     }
 }";
-            var compilation0 = CreateCompilation(source, options: TestOptions.DebugDll);
+            var compilation0 = CreateCompilation(source, options: options);
 
             WithRuntimeInstance(compilation0, runtime =>
             {
diff --git a/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/LocalsTests.cs b/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/LocalsTests.cs
index 7aebf854a16a3327147210f1ab6ecfb0adba70b6..92d992c0dbcaf00032e0c2da77a94515aa0efb8d 100644
--- a/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/LocalsTests.cs
+++ b/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/LocalsTests.cs
@@ -1628,8 +1628,9 @@ .maxstack  1
         /// Should not include "this" inside display class
         /// instance method if "this" is not captured.
         /// </summary>
-        [Fact]
-        public void NoThisInsideDisplayClassInstanceMethod()
+        [Theory]
+        [MemberData(nameof(NonNullTypesTrueAndFalseDebugDll))]
+        public void NoThisInsideDisplayClassInstanceMethod(CSharpCompilationOptions options)
         {
             var source =
 @"using System;
@@ -1647,7 +1648,7 @@ class C
         f(2)(x);
     }
 }";
-            var compilation0 = CreateCompilation(source, options: TestOptions.DebugDll);
+            var compilation0 = CreateCompilation(source, options: options);
             WithRuntimeInstance(compilation0, runtime =>
             {
                 var context = CreateMethodContext(runtime, "C.<>c__DisplayClass0_0.<M>b__0");
diff --git a/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ReferencedModulesTests.cs b/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ReferencedModulesTests.cs
index 0d796d986fcd72fbe25a00cc919e15e0f3915664..c1d181ecb603a149417d1f725080e322ad445eda 100644
--- a/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ReferencedModulesTests.cs
+++ b/src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ReferencedModulesTests.cs
@@ -1367,8 +1367,9 @@ .maxstack  1
 
         // References to missing assembly from PDB custom debug info.
         [WorkItem(13275, "https://github.com/dotnet/roslyn/issues/13275")]
-        [Fact]
-        public void CorLibWithAssemblyReferences_Pdb()
+        [Theory]
+        [MemberData(nameof(NonNullTypesTrueAndFalseReleaseDll))]
+        public void CorLibWithAssemblyReferences_Pdb(CSharpCompilationOptions options)
         {
             string sourceLib =
 @"namespace Namespace
@@ -1397,7 +1398,7 @@ public class Void : Object { }
 }";
             // Create a custom corlib with a reference to compilation
             // above and a reference to the actual mscorlib.
-            var compCorLib = CreateEmptyCompilation(sourceCorLib, assemblyName: CorLibAssemblyName, references: new[] { MscorlibRef, refLib });
+            var compCorLib = CreateEmptyCompilation(sourceCorLib, assemblyName: CorLibAssemblyName, references: new[] { MscorlibRef, refLib }, options: options);
             compCorLib.VerifyDiagnostics();
             var objectType = compCorLib.SourceAssembly.GlobalNamespace.GetMember<NamedTypeSymbol>("System.Object");
             Assert.NotNull(objectType.BaseType());