Format errors on test failure. Fixes #214.

Author: hildjj

bin/peggy-cli.mjs

@@ -545,6 +545,9 @@ export class PeggyCLI extends Command {
         sources: [{
           source: this.argv.grammarSource,
           text: input,
+        }, {
+          source: this.testGrammarSource,
+          text: this.testText,
         }],
       });
     }

test/cli/run.spec.ts

@@ -944,7 +944,13 @@ Options:
       stdin: "foo='1'",
       errorCode: "peggy.cli",
       exitCode: 2,
-      error: "end of input",
+      error: `\
+Error running test
+Error: Expected "1" but end of input found.
+ --> command line:1:1
+  |
+1 |${" "}
+  |`,
     });
   });