diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ac6c913691..52c53c6f8f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -247,6 +247,7 @@ set(TINT_TEST_SRCS
   ast/uint_literal_test.cc
   ast/unary_derivative_expression_test.cc
   ast/unary_method_expression_test.cc
+  ast/unary_op_expression_test.cc
   ast/variable_test.cc
   reader/wgsl/lexer_test.cc
   reader/wgsl/parser_test.cc
diff --git a/src/ast/unary_op_expression.cc b/src/ast/unary_op_expression.cc
index da31e8ed4b..33db0c037f 100644
--- a/src/ast/unary_op_expression.cc
+++ b/src/ast/unary_op_expression.cc
@@ -17,6 +17,8 @@
 namespace tint {
 namespace ast {
 
+UnaryOpExpression::UnaryOpExpression() : Expression() {}
+
 UnaryOpExpression::UnaryOpExpression(UnaryOp op,
                                      std::unique_ptr<Expression> expr)
     : Expression(), op_(op), expr_(std::move(expr)) {}
@@ -29,12 +31,14 @@ UnaryOpExpression::UnaryOpExpression(const Source& source,
 UnaryOpExpression::~UnaryOpExpression() = default;
 
 bool UnaryOpExpression::IsValid() const {
-  return expr_ != nullptr;
+  return expr_ != nullptr && expr_->IsValid();
 }
 
 void UnaryOpExpression::to_str(std::ostream& out, size_t indent) const {
   make_indent(out, indent);
-  out << "UnaryOp{" << op_ << std::endl;
+  out << "UnaryOp{" << std::endl;
+  make_indent(out, indent + 2);
+  out << op_ << std::endl;
   expr_->to_str(out, indent + 2);
   make_indent(out, indent);
   out << "}" << std::endl;
diff --git a/src/ast/unary_op_expression.h b/src/ast/unary_op_expression.h
index b77c185b44..934a95f5ca 100644
--- a/src/ast/unary_op_expression.h
+++ b/src/ast/unary_op_expression.h
@@ -28,6 +28,8 @@ namespace ast {
 /// A unary op expression
 class UnaryOpExpression : public Expression {
  public:
+  /// Constructor
+  UnaryOpExpression();
   /// Constructor
   /// @param op the op
   /// @param expr the expr
diff --git a/src/ast/unary_op_expression_test.cc b/src/ast/unary_op_expression_test.cc
new file mode 100644
index 0000000000..fef07d5ca3
--- /dev/null
+++ b/src/ast/unary_op_expression_test.cc
@@ -0,0 +1,80 @@
+// Copyright 2020 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/ast/unary_op_expression.h"
+
+#include <sstream>
+
+#include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
+
+namespace tint {
+namespace ast {
+
+using UnaryOpExpressionTest = testing::Test;
+
+TEST_F(UnaryOpExpressionTest, Creation) {
+  auto ident = std::make_unique<IdentifierExpression>("ident");
+  auto ident_ptr = ident.get();
+
+  UnaryOpExpression u(UnaryOp::kNot, std::move(ident));
+  EXPECT_EQ(u.op(), UnaryOp::kNot);
+  EXPECT_EQ(u.expr(), ident_ptr);
+}
+
+TEST_F(UnaryOpExpressionTest, Creation_WithSource) {
+  auto ident = std::make_unique<IdentifierExpression>("ident");
+  UnaryOpExpression u(Source{20, 2}, UnaryOp::kNot, std::move(ident));
+  auto src = u.source();
+  EXPECT_EQ(src.line, 20);
+  EXPECT_EQ(src.column, 2);
+}
+
+TEST_F(UnaryOpExpressionTest, IsUnaryOp) {
+  UnaryOpExpression u;
+  EXPECT_TRUE(u.IsUnaryOp());
+}
+
+TEST_F(UnaryOpExpressionTest, IsValid) {
+  auto ident = std::make_unique<IdentifierExpression>("ident");
+  UnaryOpExpression u(UnaryOp::kNot, std::move(ident));
+  EXPECT_TRUE(u.IsValid());
+}
+
+TEST_F(UnaryOpExpressionTest, IsValid_NullExpression) {
+  UnaryOpExpression u;
+  u.set_op(UnaryOp::kNot);
+  EXPECT_FALSE(u.IsValid());
+}
+
+TEST_F(UnaryOpExpressionTest, IsValid_InvalidExpression) {
+  auto ident = std::make_unique<IdentifierExpression>("");
+  UnaryOpExpression u(UnaryOp::kNot, std::move(ident));
+  EXPECT_FALSE(u.IsValid());
+}
+
+TEST_F(UnaryOpExpressionTest, ToStr) {
+  auto ident = std::make_unique<IdentifierExpression>("ident");
+  UnaryOpExpression u(UnaryOp::kNot, std::move(ident));
+  std::ostringstream out;
+  u.to_str(out, 2);
+  EXPECT_EQ(out.str(), R"(  UnaryOp{
+    not
+    Identifier{ident}
+  }
+)");
+}
+
+}  // namespace ast
+}  // namespace tint