Remove assert in test.

The `assert` will compile out in Release builds so we don't actually
parse the module, which means we're always testing against an empty
module and the tests fail.

Bug: tint:22
Change-Id: I49a1f8fc8ec6231a65f4f17e385cff576c4f0d06
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17204
Reviewed-by: David Neto <dneto@google.com>

src/validator_impl_import_test.cc

@@ -12,8 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include <assert.h>
-
 #include <iostream>
 
 #include "gtest/gtest.h"
@@ -26,12 +24,10 @@ namespace {
 ast::Module build_module(std::string data) {
   auto reader = std::make_unique<tint::reader::wgsl::Parser>(
       std::string(data.begin(), data.end()));
-  assert(reader->Parse());
+  EXPECT_TRUE(reader->Parse()) << reader->error();
   return reader->module();
 }
 
-}  // namespace
-
 using ValidatorImplTest = testing::Test;
 
 TEST_F(ValidatorImplTest, Import) {
@@ -59,4 +55,5 @@ TEST_F(ValidatorImplTest, Import_Fail_Typo) {
   EXPECT_EQ(v.error(), "1:1: v-0001: unknown import: GLSL.std.4501");
 }
 
+}  // namespace
 }  // namespace tint