Add a test runner executable.

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index da2192764a1af63e56830205f26e5129dc3acd06..5c12593e4f4bd8864c07210b527dab933c905340 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -13,6 +13,17 @@ import 'package:stack_trace/stack_trace.dart';
 /// The return type should only ever by [Future] or void.
 typedef AsyncFunction();
 
+/// A regular expression to match the exception prefix that some exceptions'
+/// [Object.toString] values contain.
+final _exceptionPrefix = new RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');
+
+/// Get a string description of an exception.
+///
+/// Many exceptions include the exception class name at the beginning of their
+/// [toString], so we remove that if it exists.
+String getErrorMessage(error) =>
+  error.toString().replaceFirst(_exceptionPrefix, '');
+
 /// Indent each line in [str] by two spaces.
 String indent(String str) =>
     str.replaceAll(new RegExp("^", multiLine: true), "  ");
@@ -34,6 +45,25 @@ class Pair<E, F> {
   int get hashCode => first.hashCode ^ last.hashCode;
 }
 
+/// A regular expression matching the path to a temporary file used to start an
+/// isolate.
+///
+/// These paths aren't relevant and are removed from stack traces.
+final _isolatePath =
+    new RegExp(r"/unittest_[A-Za-z0-9]{6}/runInIsolate\.dart$");
+
+/// Returns [stackTrace] converted to a [Chain] with all irrelevant frames
+/// folded together.
+Chain terseChain(StackTrace stackTrace) {
+  return new Chain.forTrace(stackTrace).foldFrames((frame) {
+    if (frame.package == 'unittest') return true;
+
+    // Filter out frames from our isolate bootstrap as well.
+    if (frame.uri.scheme != 'file') return false;
+    return frame.uri.path.contains(_isolatePath);
+  }, terse: true);
+}
+
 /// Returns a Trace object from a StackTrace object or a String, or the
 /// unchanged input if formatStacks is false;
 Trace getTrace(stack, bool formatStacks, bool filterStacks) {