Update the testing harness to insulate tests in --nofork mode.

Before, when running a test binary in --nofork mode, it was up to the
test to reset the program state before exiting to avoid dependencies on
other tests. Now after each test the test harness will:

1. Wipeout the fake environmennt.
2. Reset the data segment to its initialization state.

This achieves reasonable insulation between tests even though certain
things (like a segfault) are stil not practical to completely insulate
without fork()'ing.

1 files changed, 22 insertions, 0 deletions

diff --git a/02-usart/tests/metatest.c b/02-usart/tests/metatest.c
new file mode 100644
index 0000000..1024156
--- /dev/null
+++ b/02-usart/tests/metatest.c
@@ -0,0 +1,22 @@
+#include "test_harness.h"
+
+/* Tests the test harness itself. */
+
+static int my_variable;
+static int my_initialized_variable = 5;
+
+TEST(meta, clobbers_variables)
+{
+  my_variable = 6;
+  my_initialized_variable = 5;
+
+  return 0;
+}
+
+TEST(meta, variables_reset)
+{
+  ASSERT_EQ(my_variable, 0);
+  ASSERT_EQ(my_initialized_variable, 5);
+
+  return 0;
+}