diff --git a/src/type_determiner_test.cc b/src/type_determiner_test.cc
index d59d21f..c999d85 100644
--- a/src/type_determiner_test.cc
+++ b/src/type_determiner_test.cc
@@ -68,17 +68,25 @@
   void to_str(std::ostream&, size_t) const override {}
 };
 
-class TypeDeterminerTest : public testing::Test {
+class TypeDeterminerHelper {
  public:
-  void SetUp() override { td_ = std::make_unique<TypeDeterminer>(&ctx_); }
+  TypeDeterminerHelper() : td_(std::make_unique<TypeDeterminer>(&ctx_)) {}
 
   TypeDeterminer* td() const { return td_.get(); }
+  ast::Module* mod() { return &mod_; }
 
  private:
   Context ctx_;
+  ast::Module mod_;
   std::unique_ptr<TypeDeterminer> td_;
 };
 
+class TypeDeterminerTest : public TypeDeterminerHelper, public testing::Test {};
+
+template <typename T>
+class TypeDeterminerTestWithParam : public TypeDeterminerHelper,
+                                    public testing::TestWithParam<T> {};
+
 TEST_F(TypeDeterminerTest, Error_WithEmptySource) {
   FakeStmt s;
   s.set_source(Source{0, 0});
@@ -422,14 +430,12 @@
 
   auto idx = std::make_unique<ast::ScalarConstructorExpression>(
       std::make_unique<ast::IntLiteral>(&i32, 2));
-
-  ast::Module m;
   auto var =
       std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone, &ary);
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::ArrayAccessorExpression acc(
       std::make_unique<ast::IdentifierExpression>("my_var"), std::move(idx));
@@ -445,14 +451,12 @@
 
   auto idx = std::make_unique<ast::ScalarConstructorExpression>(
       std::make_unique<ast::IntLiteral>(&i32, 2));
-
-  ast::Module m;
   auto var =
       std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone, &mat);
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::ArrayAccessorExpression acc(
       std::make_unique<ast::IdentifierExpression>("my_var"), std::move(idx));
@@ -471,14 +475,12 @@
       std::make_unique<ast::IntLiteral>(&i32, 2));
   auto idx2 = std::make_unique<ast::ScalarConstructorExpression>(
       std::make_unique<ast::IntLiteral>(&i32, 1));
-
-  ast::Module m;
   auto var =
       std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone, &mat);
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::ArrayAccessorExpression acc(
       std::make_unique<ast::ArrayAccessorExpression>(
@@ -498,14 +500,12 @@
 
   auto idx = std::make_unique<ast::ScalarConstructorExpression>(
       std::make_unique<ast::IntLiteral>(&i32, 2));
-
-  ast::Module m;
   auto var =
       std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone, &vec);
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::ArrayAccessorExpression acc(
       std::make_unique<ast::IdentifierExpression>("my_var"), std::move(idx));
@@ -530,11 +530,10 @@
   ast::VariableList params;
   auto func =
       std::make_unique<ast::Function>("my_func", std::move(params), &f32);
-  ast::Module m;
-  m.AddFunction(std::move(func));
+  mod()->AddFunction(std::move(func));
 
   // Register the function
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::ExpressionList call_params;
   ast::CallExpression call(
@@ -551,11 +550,10 @@
   ast::VariableList params;
   auto func =
       std::make_unique<ast::Function>("my_func", std::move(params), &f32);
-  ast::Module m;
-  m.AddFunction(std::move(func));
+  mod()->AddFunction(std::move(func));
 
   // Register the function
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::ExpressionList call_params;
   call_params.push_back(std::make_unique<ast::ScalarConstructorExpression>(
@@ -614,14 +612,12 @@
 
 TEST_F(TypeDeterminerTest, Expr_Identifier_GlobalVariable) {
   ast::type::F32Type f32;
-
-  ast::Module m;
   auto var =
       std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone, &f32);
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::IdentifierExpression ident("my_var");
   EXPECT_TRUE(td()->DetermineResultType(&ident));
@@ -659,11 +655,10 @@
   ast::VariableList params;
   auto func =
       std::make_unique<ast::Function>("my_func", std::move(params), &f32);
-  ast::Module m;
-  m.AddFunction(std::move(func));
+  mod()->AddFunction(std::move(func));
 
   // Register the function
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   ast::IdentifierExpression ident("my_func");
   EXPECT_TRUE(td()->DetermineResultType(&ident));
@@ -690,11 +685,10 @@
   auto var = std::make_unique<ast::Variable>("my_struct",
                                              ast::StorageClass::kNone, &st);
 
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   auto ident = std::make_unique<ast::IdentifierExpression>("my_struct");
   auto mem_ident = std::make_unique<ast::IdentifierExpression>("second_member");
@@ -711,11 +705,10 @@
 
   auto var = std::make_unique<ast::Variable>("my_vec", ast::StorageClass::kNone,
                                              &vec3);
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   auto ident = std::make_unique<ast::IdentifierExpression>("my_vec");
   auto swizzle = std::make_unique<ast::IdentifierExpression>("xy");
@@ -780,12 +773,10 @@
 
   auto var =
       std::make_unique<ast::Variable>("c", ast::StorageClass::kNone, &stA);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td()->Determine(&m));
+  EXPECT_TRUE(td()->Determine(mod()));
 
   auto ident = std::make_unique<ast::IdentifierExpression>("c");
   auto mem_ident = std::make_unique<ast::IdentifierExpression>("mem");
@@ -809,7 +800,7 @@
   EXPECT_EQ(mem.result_type()->AsVector()->size(), 2u);
 }
 
-using Expr_Binary_BitwiseTest = testing::TestWithParam<ast::BinaryOp>;
+using Expr_Binary_BitwiseTest = TypeDeterminerTestWithParam<ast::BinaryOp>;
 TEST_P(Expr_Binary_BitwiseTest, Scalar) {
   auto op = GetParam();
 
@@ -817,21 +808,16 @@
 
   auto var =
       std::make_unique<ast::Variable>("val", ast::StorageClass::kNone, &i32);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine(mod())) << td()->error();
 
   ast::BinaryExpression expr(
       op, std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   EXPECT_TRUE(expr.result_type()->IsI32());
 }
@@ -844,21 +830,16 @@
 
   auto var =
       std::make_unique<ast::Variable>("val", ast::StorageClass::kNone, &vec3);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine(mod())) << td()->error();
 
   ast::BinaryExpression expr(
       op, std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsI32());
@@ -877,7 +858,7 @@
                                          ast::BinaryOp::kDivide,
                                          ast::BinaryOp::kModulo));
 
-using Expr_Binary_LogicalTest = testing::TestWithParam<ast::BinaryOp>;
+using Expr_Binary_LogicalTest = TypeDeterminerTestWithParam<ast::BinaryOp>;
 TEST_P(Expr_Binary_LogicalTest, Scalar) {
   auto op = GetParam();
 
@@ -885,21 +866,16 @@
 
   auto var = std::make_unique<ast::Variable>("val", ast::StorageClass::kNone,
                                              &bool_type);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       op, std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   EXPECT_TRUE(expr.result_type()->IsBool());
 }
@@ -912,21 +888,16 @@
 
   auto var =
       std::make_unique<ast::Variable>("val", ast::StorageClass::kNone, &vec3);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine(mod())) << td()->error();
 
   ast::BinaryExpression expr(
       op, std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsBool());
@@ -937,7 +908,7 @@
                          testing::Values(ast::BinaryOp::kLogicalAnd,
                                          ast::BinaryOp::kLogicalOr));
 
-using Expr_Binary_CompareTest = testing::TestWithParam<ast::BinaryOp>;
+using Expr_Binary_CompareTest = TypeDeterminerTestWithParam<ast::BinaryOp>;
 TEST_P(Expr_Binary_CompareTest, Scalar) {
   auto op = GetParam();
 
@@ -945,21 +916,16 @@
 
   auto var =
       std::make_unique<ast::Variable>("val", ast::StorageClass::kNone, &i32);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       op, std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   EXPECT_TRUE(expr.result_type()->IsBool());
 }
@@ -972,21 +938,16 @@
 
   auto var =
       std::make_unique<ast::Variable>("val", ast::StorageClass::kNone, &vec3);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       op, std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsBool());
@@ -1006,22 +967,17 @@
 
   auto var =
       std::make_unique<ast::Variable>("val", ast::StorageClass::kNone, &i32);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("val"),
       std::make_unique<ast::IdentifierExpression>("val"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   EXPECT_TRUE(expr.result_type()->IsI32());
 }
@@ -1034,23 +990,18 @@
       std::make_unique<ast::Variable>("scalar", ast::StorageClass::kNone, &f32);
   auto vector = std::make_unique<ast::Variable>(
       "vector", ast::StorageClass::kNone, &vec3);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(scalar));
-  m.AddGlobalVariable(std::move(vector));
+  mod()->AddGlobalVariable(std::move(scalar));
+  mod()->AddGlobalVariable(std::move(vector));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("vector"),
       std::make_unique<ast::IdentifierExpression>("scalar"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsF32());
@@ -1065,23 +1016,18 @@
       std::make_unique<ast::Variable>("scalar", ast::StorageClass::kNone, &f32);
   auto vector = std::make_unique<ast::Variable>(
       "vector", ast::StorageClass::kNone, &vec3);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(scalar));
-  m.AddGlobalVariable(std::move(vector));
+  mod()->AddGlobalVariable(std::move(scalar));
+  mod()->AddGlobalVariable(std::move(vector));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("scalar"),
       std::make_unique<ast::IdentifierExpression>("vector"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsF32());
@@ -1094,22 +1040,17 @@
 
   auto vector = std::make_unique<ast::Variable>(
       "vector", ast::StorageClass::kNone, &vec3);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(vector));
+  mod()->AddGlobalVariable(std::move(vector));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("vector"),
       std::make_unique<ast::IdentifierExpression>("vector"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsF32());
@@ -1124,23 +1065,18 @@
       std::make_unique<ast::Variable>("scalar", ast::StorageClass::kNone, &f32);
   auto matrix = std::make_unique<ast::Variable>(
       "matrix", ast::StorageClass::kNone, &mat3x2);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(scalar));
-  m.AddGlobalVariable(std::move(matrix));
+  mod()->AddGlobalVariable(std::move(scalar));
+  mod()->AddGlobalVariable(std::move(matrix));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("matrix"),
       std::make_unique<ast::IdentifierExpression>("scalar"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsMatrix());
 
@@ -1158,23 +1094,18 @@
       std::make_unique<ast::Variable>("scalar", ast::StorageClass::kNone, &f32);
   auto matrix = std::make_unique<ast::Variable>(
       "matrix", ast::StorageClass::kNone, &mat3x2);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(scalar));
-  m.AddGlobalVariable(std::move(matrix));
+  mod()->AddGlobalVariable(std::move(scalar));
+  mod()->AddGlobalVariable(std::move(matrix));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("scalar"),
       std::make_unique<ast::IdentifierExpression>("matrix"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsMatrix());
 
@@ -1193,23 +1124,18 @@
       "vector", ast::StorageClass::kNone, &vec3);
   auto matrix = std::make_unique<ast::Variable>(
       "matrix", ast::StorageClass::kNone, &mat3x2);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(vector));
-  m.AddGlobalVariable(std::move(matrix));
+  mod()->AddGlobalVariable(std::move(vector));
+  mod()->AddGlobalVariable(std::move(matrix));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("matrix"),
       std::make_unique<ast::IdentifierExpression>("vector"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsF32());
@@ -1225,23 +1151,18 @@
       "vector", ast::StorageClass::kNone, &vec3);
   auto matrix = std::make_unique<ast::Variable>(
       "matrix", ast::StorageClass::kNone, &mat3x2);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(vector));
-  m.AddGlobalVariable(std::move(matrix));
+  mod()->AddGlobalVariable(std::move(vector));
+  mod()->AddGlobalVariable(std::move(matrix));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("vector"),
       std::make_unique<ast::IdentifierExpression>("matrix"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsVector());
   EXPECT_TRUE(expr.result_type()->AsVector()->type()->IsF32());
@@ -1257,23 +1178,18 @@
       "mat4x3", ast::StorageClass::kNone, &mat4x3);
   auto matrix2 = std::make_unique<ast::Variable>(
       "mat3x4", ast::StorageClass::kNone, &mat3x4);
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(matrix1));
-  m.AddGlobalVariable(std::move(matrix2));
+  mod()->AddGlobalVariable(std::move(matrix1));
+  mod()->AddGlobalVariable(std::move(matrix2));
 
   // Register the global
-  ASSERT_TRUE(td.Determine(&m)) << td.error();
+  ASSERT_TRUE(td()->Determine((mod()))) << td()->error();
 
   ast::BinaryExpression expr(
       ast::BinaryOp::kMultiply,
       std::make_unique<ast::IdentifierExpression>("mat4x3"),
       std::make_unique<ast::IdentifierExpression>("mat3x4"));
 
-  ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();
+  ASSERT_TRUE(td()->DetermineResultType(&expr)) << td()->error();
   ASSERT_NE(expr.result_type(), nullptr);
   ASSERT_TRUE(expr.result_type()->IsMatrix());
 
@@ -1284,7 +1200,7 @@
 }
 
 using UnaryDerivativeExpressionTest =
-    testing::TestWithParam<ast::UnaryDerivative>;
+    TypeDeterminerTestWithParam<ast::UnaryDerivative>;
 TEST_P(UnaryDerivativeExpressionTest, Expr_UnaryDerivative) {
   auto derivative = GetParam();
 
@@ -1294,20 +1210,15 @@
 
   auto var =
       std::make_unique<ast::Variable>("ident", ast::StorageClass::kNone, &vec4);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
   ast::UnaryDerivativeExpression der(
       derivative, ast::DerivativeModifier::kNone,
       std::make_unique<ast::IdentifierExpression>("ident"));
-  EXPECT_TRUE(td.DetermineResultType(&der));
+  EXPECT_TRUE(td()->DetermineResultType(&der));
   ASSERT_NE(der.result_type(), nullptr);
   ASSERT_TRUE(der.result_type()->IsVector());
   EXPECT_TRUE(der.result_type()->AsVector()->type()->IsF32());
@@ -1319,7 +1230,8 @@
                                          ast::UnaryDerivative::kDpdy,
                                          ast::UnaryDerivative::kFwidth));
 
-using UnaryMethodExpressionBoolTest = testing::TestWithParam<ast::UnaryMethod>;
+using UnaryMethodExpressionBoolTest =
+    TypeDeterminerTestWithParam<ast::UnaryMethod>;
 TEST_P(UnaryMethodExpressionBoolTest, Expr_UnaryMethod_Any) {
   auto op = GetParam();
 
@@ -1328,22 +1240,17 @@
 
   auto var = std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone,
                                              &vec3);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   ast::ExpressionList params;
   params.push_back(std::make_unique<ast::IdentifierExpression>("my_var"));
 
   ast::UnaryMethodExpression exp(op, std::move(params));
 
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
   // Register the variable
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
-  EXPECT_TRUE(td.DetermineResultType(&exp));
+  EXPECT_TRUE(td()->DetermineResultType(&exp));
   ASSERT_NE(exp.result_type(), nullptr);
   EXPECT_TRUE(exp.result_type()->IsBool());
 }
@@ -1352,7 +1259,8 @@
                          testing::Values(ast::UnaryMethod::kAny,
                                          ast::UnaryMethod::kAll));
 
-using UnaryMethodExpressionVecTest = testing::TestWithParam<ast::UnaryMethod>;
+using UnaryMethodExpressionVecTest =
+    TypeDeterminerTestWithParam<ast::UnaryMethod>;
 TEST_P(UnaryMethodExpressionVecTest, Expr_UnaryMethod_Bool) {
   auto op = GetParam();
 
@@ -1361,22 +1269,17 @@
 
   auto var = std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone,
                                              &vec3);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   ast::ExpressionList params;
   params.push_back(std::make_unique<ast::IdentifierExpression>("my_var"));
 
   ast::UnaryMethodExpression exp(op, std::move(params));
 
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
   // Register the variable
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
-  EXPECT_TRUE(td.DetermineResultType(&exp));
+  EXPECT_TRUE(td()->DetermineResultType(&exp));
   ASSERT_NE(exp.result_type(), nullptr);
   ASSERT_TRUE(exp.result_type()->IsVector());
   EXPECT_TRUE(exp.result_type()->AsVector()->type()->IsBool());
@@ -1389,22 +1292,17 @@
 
   auto var =
       std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone, &f32);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   ast::ExpressionList params;
   params.push_back(std::make_unique<ast::IdentifierExpression>("my_var"));
 
   ast::UnaryMethodExpression exp(op, std::move(params));
 
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
   // Register the variable
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
-  EXPECT_TRUE(td.DetermineResultType(&exp));
+  EXPECT_TRUE(td()->DetermineResultType(&exp));
   ASSERT_NE(exp.result_type(), nullptr);
   EXPECT_TRUE(exp.result_type()->IsBool());
 }
@@ -1421,9 +1319,7 @@
 
   auto var = std::make_unique<ast::Variable>("my_var", ast::StorageClass::kNone,
                                              &vec3);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
+  mod()->AddGlobalVariable(std::move(var));
 
   ast::ExpressionList params;
   params.push_back(std::make_unique<ast::IdentifierExpression>("my_var"));
@@ -1431,13 +1327,10 @@
 
   ast::UnaryMethodExpression exp(ast::UnaryMethod::kDot, std::move(params));
 
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
   // Register the variable
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
-  EXPECT_TRUE(td.DetermineResultType(&exp));
+  EXPECT_TRUE(td()->DetermineResultType(&exp));
   ASSERT_NE(exp.result_type(), nullptr);
   EXPECT_TRUE(exp.result_type()->IsF32());
 }
@@ -1451,10 +1344,8 @@
       std::make_unique<ast::Variable>("v3", ast::StorageClass::kNone, &vec3);
   auto var2 =
       std::make_unique<ast::Variable>("v2", ast::StorageClass::kNone, &vec2);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var1));
-  m.AddGlobalVariable(std::move(var2));
+  mod()->AddGlobalVariable(std::move(var1));
+  mod()->AddGlobalVariable(std::move(var2));
 
   ast::ExpressionList params;
   params.push_back(std::make_unique<ast::IdentifierExpression>("v3"));
@@ -1463,13 +1354,10 @@
   ast::UnaryMethodExpression exp(ast::UnaryMethod::kOuterProduct,
                                  std::move(params));
 
-  Context ctx;
-  TypeDeterminer td(&ctx);
-
   // Register the variable
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
-  EXPECT_TRUE(td.DetermineResultType(&exp));
+  EXPECT_TRUE(td()->DetermineResultType(&exp));
   ASSERT_NE(exp.result_type(), nullptr);
   ASSERT_TRUE(exp.result_type()->IsMatrix());
   auto* mat = exp.result_type()->AsMatrix();
@@ -1478,7 +1366,7 @@
   EXPECT_EQ(mat->columns(), 2u);
 }
 
-using UnaryOpExpressionTest = testing::TestWithParam<ast::UnaryOp>;
+using UnaryOpExpressionTest = TypeDeterminerTestWithParam<ast::UnaryOp>;
 TEST_P(UnaryOpExpressionTest, Expr_UnaryOp) {
   auto op = GetParam();
 
@@ -1488,19 +1376,14 @@
 
   auto var =
       std::make_unique<ast::Variable>("ident", ast::StorageClass::kNone, &vec4);
-
-  ast::Module m;
-  m.AddGlobalVariable(std::move(var));
-
-  Context ctx;
-  TypeDeterminer td(&ctx);
+  mod()->AddGlobalVariable(std::move(var));
 
   // Register the global
-  EXPECT_TRUE(td.Determine(&m));
+  EXPECT_TRUE(td()->Determine((mod())));
 
   ast::UnaryOpExpression der(
       op, std::make_unique<ast::IdentifierExpression>("ident"));
-  EXPECT_TRUE(td.DetermineResultType(&der));
+  EXPECT_TRUE(td()->DetermineResultType(&der));
   ASSERT_NE(der.result_type(), nullptr);
   ASSERT_TRUE(der.result_type()->IsVector());
   EXPECT_TRUE(der.result_type()->AsVector()->type()->IsF32());
@@ -1525,10 +1408,9 @@
   stmts.push_back(std::move(stmt));
   func->set_body(std::move(stmts));
 
-  ast::Module m;
-  m.AddFunction(std::move(func));
+  mod()->AddFunction(std::move(func));
 
-  EXPECT_TRUE(td()->Determine(&m)) << td()->error();
+  EXPECT_TRUE(td()->Determine((mod()))) << td()->error();
   EXPECT_EQ(var_ptr->storage_class(), ast::StorageClass::kFunction);
 }
 
@@ -1547,10 +1429,9 @@
   stmts.push_back(std::move(stmt));
   func->set_body(std::move(stmts));
 
-  ast::Module m;
-  m.AddFunction(std::move(func));
+  mod()->AddFunction(std::move(func));
 
-  EXPECT_TRUE(td()->Determine(&m)) << td()->error();
+  EXPECT_TRUE(td()->Determine((mod()))) << td()->error();
   EXPECT_EQ(var_ptr->storage_class(), ast::StorageClass::kNone);
 }
 
@@ -1567,10 +1448,9 @@
   stmts.push_back(std::move(stmt));
   func->set_body(std::move(stmts));
 
-  ast::Module m;
-  m.AddFunction(std::move(func));
+  mod()->AddFunction(std::move(func));
 
-  EXPECT_FALSE(td()->Determine(&m));
+  EXPECT_FALSE(td()->Determine((mod())));
   EXPECT_EQ(td()->error(),
             "function variable has a non-function storage class");
 }