Sane use of test_expect_failure

Originally, test_expect_failure was designed to be the opposite
of test_expect_success, but this was a bad decision.  Most tests
run a series of commands that leads to the single command that
needs to be tested, like this:

    test_expect_{success,failure} 'test title' '
	setup1 &&
        setup2 &&
        setup3 &&
        what is to be tested
    '

And expecting a failure exit from the whole sequence misses the
point of writing tests.  Your setup$N that are supposed to
succeed may have failed without even reaching what you are
trying to test.  The only valid use of test_expect_failure is to
check a trivial single command that is expected to fail, which
is a minority in tests of Porcelain-ish commands.

This large-ish patch rewrites all uses of test_expect_failure to
use test_expect_success and rewrites the condition of what is
tested, like this:

    test_expect_success 'test title' '
	setup1 &&
        setup2 &&
        setup3 &&
        ! this command should fail
    '

test_expect_failure is redefined to serve as a reminder that
that test *should* succeed but due to a known breakage in git it
currently does not pass.  So if git-foo command should create a
file 'bar' but you discovered a bug that it doesn't, you can
write a test like this:

    test_expect_failure 'git-foo should create bar' '
        rm -f bar &&
        git foo &&
        test -f bar
    '

This construct acts similar to test_expect_success, but instead
of reporting "ok/FAIL" like test_expect_success does, the
outcome is reported as "FIXED/still broken".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/t/t7001-mv.sh b/t/t7001-mv.sh
index b730c900b1..b1243b4163 100755
--- a/t/t7001-mv.sh
+++ b/t/t7001-mv.sh
@@ -78,9 +78,9 @@ test_expect_success \
      git diff-tree -r -M --name-status  HEAD^ HEAD | \
      grep "^R100..*path2/README..*path1/path2/README"'
 
-test_expect_failure \
+test_expect_success \
     'do not move directory over existing directory' \
-    'mkdir path0 && mkdir path0/path2 && git mv path2 path0'
+    'mkdir path0 && mkdir path0/path2 && ! git mv path2 path0'
 
 test_expect_success \
     'move into "."' \