Fix issues with json files

File parsing no longer uses istream, which strips whitespace. Moved hard-coded json to its own file.

Signed-off-by: Alexander Yee <xander.yee@gmail.com>
Change-Id: I342b74fd1cc8c5af7721af5955aa7d7b185ac71e
diff --git a/frc971/constants/constants_sender_test.cc b/frc971/constants/constants_sender_test.cc
index 1441767..512cb68 100644
--- a/frc971/constants/constants_sender_test.cc
+++ b/frc971/constants/constants_sender_test.cc
@@ -113,11 +113,11 @@
       ({
         ConstantSender<testdata::ConstantsData, testdata::ConstantsList>
             test_syntax(constants_sender_event_loop_.get(),
-                        "frc971/constants/testdata/syntaxerror.json", 971,
+                        "frc971/constants/testdata/syntax_error.json", 971,
                         "/constants");
         event_loop_factory_.RunFor(std::chrono::seconds(1));
       }),
-      "Error on line 0");
+      "Invalid field name");
 }
 
 }  // namespace testing