[PATCH 4/5] test: hush: Add test for command substitution

[Sean Anderson]

This adds a basic test for command substitution. A more advanced test
currently fails, and is left commented-out for now. A basic example of the
difference is that in bash

	$ a=b; echo a=$(echo $a)
	b

but in hush

	=> a=b; echo a=$(echo $a)
	a=

This is because command substitution takes place during parsing, before any
of the rest of the command has been executed.

Signed-off-by: Sean Anderson <seanga2 at gmail.com>
---

 test/cmd/test_echo.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/test/cmd/test_echo.c b/test/cmd/test_echo.c
index 13e1fb7c82..f3d44d840d 100644
--- a/test/cmd/test_echo.c
+++ b/test/cmd/test_echo.c
@@ -31,13 +31,21 @@ static struct test_data echo_data[] = {
 	 * j, q, x are among the least frequent letters in English.
 	 * Hence no collision for the variable name jQx is expected.
 	 */
-	{"setenv jQx X; echo \"a)\" ${jQx} 'b)' '${jQx}' c) ${jQx}; setenv jQx",
+	{"setenv jQx X; echo \"a)\" ${jQx} 'b)' '${jQx}' c\\) ${jQx}; setenv jQx",
 	 "a) X b) ${jQx} c) X"},
 	/* Test shell variable assignments without substitutions */
 	{"foo=bar echo baz", "baz"},
 	/* Test handling of shell variables. */
 	{"setenv jQx; for jQx in 1 2 3; do echo -n \"${jQx}, \"; done; echo;",
 	 "1, 2, 3, "},
+	/* Test basic command substitution */
+	{"jQx=3 echo 1 $(echo 2) $jQx", "1 2 3"},
+	/*
+	 * The following test fails because the subshell is evaluated before
+	 * anything else, but the jQx2 assignment should happen beforehand
+	 */
+	//{"jQx2=2; echo 1 $(echo ${jQx2}) 3",
+	//"1 2 3"},
 };
 
 static int lib_test_hush_echo(struct unit_test_state *uts)
-- 
2.30.1