Fix bug in the unittest's withTestEnvironment package and apply more feedback from nweiz.

pkg/unittest/lib/src/test_environment.dart

Index: pkg/unittest/lib/src/test_environment.dart
diff --git a/pkg/unittest/lib/src/test_environment.dart b/pkg/unittest/lib/src/test_environment.dart
index 444576695f3c48917424b3e2d5d1f0ab6cd446e4..ebb39bdc5e4ab087ae00b2a3439754810e49a332 100644
--- a/pkg/unittest/lib/src/test_environment.dart
+++ b/pkg/unittest/lib/src/test_environment.dart
@@ -21,9 +21,9 @@ class _TestEnvironment {
   /// The [currentTestCaseIndex] represents the index of the currently running
   /// test case.
   ///
-  /// == -1 implies the test system is not running.
-  /// == [number of test cases] is a short-lived state flagging that the last
-  ///    test has completed.
+  /// If this is -1 it implies the test system is not running.
+  /// It will be set to [number of test cases] as a short-lived state flagging
+  /// that the last test has completed.
   int currentTestCaseIndex = -1;
 
   /// The [initialized] variable specifies whether the framework