[tint] Use consistent file pattern for test files

Always append with _test.* for files to be used in tests.

Change-Id: Ide629f6974afeca5c30227c5808cd97d2ee75585
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/143402
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/src/tint/lang/wgsl/ast/call_expression_test.cc b/src/tint/lang/wgsl/ast/call_expression_test.cc
index c80e582..ba99950 100644
--- a/src/tint/lang/wgsl/ast/call_expression_test.cc
+++ b/src/tint/lang/wgsl/ast/call_expression_test.cc
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 #include "gtest/gtest-spi.h"
-#include "src/tint/lang/wgsl/ast/test_helper.h"
+#include "src/tint/lang/wgsl/ast/helper_test.h"
 
 namespace tint::ast {
 namespace {