util_test: Don’t crash when run from the wrong location

util/net/http_multipart_builder_test.cc

Index: util/net/http_multipart_builder_test.cc
diff --git a/util/net/http_multipart_builder_test.cc b/util/net/http_multipart_builder_test.cc
index 761580e7b20536fd49b0dce2630adb7e467c815f..1e8d59458f7ff8d92375716167cd5e649c2b7c4f 100644
--- a/util/net/http_multipart_builder_test.cc
+++ b/util/net/http_multipart_builder_test.cc
@@ -110,6 +110,7 @@ TEST(HTTPMultipartBuilder, ThreeFileAttachments) {
   ASSERT_TRUE(body.get());
   std::string contents = ReadStreamToString(body.get());
   auto lines = SplitCRLF(contents);
+  ASSERT_EQ(16u, lines.size());
   auto lines_it = lines.begin();
 
   const std::string& boundary = *lines_it++;
@@ -184,6 +185,7 @@ TEST(HTTPMultipartBuilder, OverwriteFileAttachment) {
   ASSERT_TRUE(body.get());
   std::string contents = ReadStreamToString(body.get());
   auto lines = SplitCRLF(contents);
+  ASSERT_EQ(15u, lines.size());
   auto lines_it = lines.begin();
 
   const std::string& boundary = *lines_it++;