Added `not' expectation

Simply negates the result of whatever expectation it is given

src/expect-core

@@ -66,3 +66,8 @@ _expect--be() { _proxy-to "$@"; }
 _expect--succeed() { test "$1" -eq 0; }
 _expect--fail()    { test "$1" -ne 0; }
 
+
+##
+# Inverts the result of an expectation represented by the remainder clause
+_expect--not() { ! _proxy-to "$@"; }
+

test/test-expect-core

@@ -63,6 +63,19 @@ describe fail
 end
 
 
+describe not
+  it will invert the result of an expectation
+    # exit code of 1, so normally `succeed' would fail
+    expect _expect--not 1 2 succeed
+      to succeed
+
+    # exit code of 0, so normally `succeed' would succeed
+    expect _expect--not 0 2 succeed
+      to fail
+  end
+end
+
+
 describe output
   it will default to asserting against stdout
     expect _expect--output 0 2 "test string" <<< "test string"