test: fix mishandling of "test '(' = '('" and similar

function                                             old     new   delta
test_main                                            246     350    +104

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/testsuite/test.tests b/testsuite/test.tests
index 2c92e34..1c2edaf 100755
--- a/testsuite/test.tests
+++ b/testsuite/test.tests
@@ -76,4 +76,24 @@
 	"0\n" \
 	"" ""
 
+testing "test '!' = '!': should be true (0)" \
+	"busybox test '!' = '!'; echo \$?" \
+	"0\n" \
+	"" ""
+
+testing "test '(' = '(': should be true (0)" \
+	"busybox test '(' = '('; echo \$?" \
+	"0\n" \
+	"" ""
+
+testing "test '!' '!' = '!': should be false (1)" \
+	"busybox test '!' '!' = '!'; echo \$?" \
+	"1\n" \
+	"" ""
+
+testing "test '!' '(' = '(': should be false (1)" \
+	"busybox test '!' '(' = '('; echo \$?" \
+	"1\n" \
+	"" ""
+
 exit $FAILCOUNT