test: Add `test_emacs_expect_t'.

Add a new test function to allow simpler testing of emacs
functionality.

`test_emacs_expect_t' takes one argument - a lisp expression to
evaluate. The test passes if the expression returns `t', otherwise it
fails and the output is reported to the tester.

test/README

@@ -202,6 +202,14 @@ library for your script to use.
    tests that may run in the same Emacs instance.  Use `let' instead
    so the scope of the changed variables is limited to a single test.
 
+ test_emacs_expect_t <emacs-lisp-expressions>
+
+  This function executes the provided emacs lisp script within
+  emacs in a manner similar to 'test_emacs'. The expressions should
+  return the value `t' to indicate that the test has passed. If the
+  test does not return `t' then it is considered failed and all data
+  returned by the test is reported to the tester.
+
  test_done
 
    Your test script must have test_done at the end.  Its purpose

test/emacs-test-functions.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+test_description="emacs test function sanity"
+. test-lib.sh
+
+test_begin_subtest "emacs test function sanity"
+test_emacs_expect_t 't'
+
+test_done

test/notmuch-test

@@ -52,6 +52,7 @@ TESTS="
   python
   hooks
   argument-parsing
+  emacs-test-functions.sh
 "
 TESTS=${NOTMUCH_TESTS:=$TESTS}
 

test/test-lib.el

@@ -83,3 +83,12 @@ nothing."
 
 (add-hook-counter 'notmuch-hello-mode-hook)
 (add-hook-counter 'notmuch-hello-refresh-hook)
+
+(defmacro notmuch-test-run (&rest body)
+  "Evaluate a BODY of test expressions and output the result."
+  `(with-temp-buffer
+     (let ((result (progn ,@body)))
+       (insert (if (stringp result)
+		   result
+		 (prin1-to-string result)))
+       (test-output))))

test/test-lib.sh

@@ -503,6 +503,35 @@ test_expect_equal_file ()
     fi
 }
 
+test_emacs_expect_t () {
+	test "$#" = 2 && { prereq=$1; shift; } || prereq=
+	test "$#" = 1 ||
+	error "bug in the test script: not 1 or 2 parameters to test_emacs_expect_t"
+
+	# Run the test.
+	if ! test_skip "$test_subtest_name"
+	then
+		test_emacs "(notmuch-test-run $1)" >/dev/null
+
+		# Restore state after the test.
+		exec 1>&6 2>&7		# Restore stdout and stderr
+		inside_subtest=
+
+		# Report success/failure.
+		result=$(cat OUTPUT)
+		if [ "$result" = t ]
+		then
+			test_ok_ "$test_subtest_name"
+		else
+			test_failure_ "$test_subtest_name" "${result}"
+		fi
+	else
+		# Restore state after the (non) test.
+		exec 1>&6 2>&7		# Restore stdout and stderr
+		inside_subtest=
+	fi
+}
+
 NOTMUCH_NEW ()
 {
     notmuch new | grep -v -E -e '^Processed [0-9]*( total)? file|Found [0-9]* total file'