test: exit with nonzero value when not all tests completed successfully

If any of the tests in our test system is not passing the execution
of the test suite completes with nonzero exit value.

It is better to rely on the exit value of the test system instead
of some arbitrary strings in test output (or use both).

test/aggregate-results.sh

@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 
+set -eu
+
 fixed=0
 success=0
 failed=0
@@ -79,3 +81,10 @@ if [ "$skipped" != "0" ]; then
     tests=$(pluralize "test" $skipped)
     echo "$skipped $tests skipped."
 fi
+
+if [ $success -gt 0 -a $fixed -eq 0 -a $failed -eq 0 -a $skipped -eq 0 ]
+then
+    exit 0
+else
+    exit 1
+fi

test/notmuch-test

@@ -97,6 +97,9 @@ trap - HUP INT TERM
 
 # Report results
 ./aggregate-results.sh test-results/*
+ev=$?
 
 # Clean up
 rm -rf test-results corpus.mail
+
+exit $ev