add tests for rehash, whence, which

test/shell.bats

@@ -22,14 +22,13 @@ load test_helper
 
 @test "shell change invalid version" {
   run rbenv-sh-shell 1.2.3
-  assert_failure
-  assert_line "rbenv: version \`1.2.3' not installed"
-  assert_line "return 1"
+  assert_failure "\
+    rbenv: version \`1.2.3' not installed
+    return 1"
 }
 
 @test "shell change version" {
   mkdir -p "${RBENV_ROOT}/versions/1.2.3"
   run rbenv-sh-shell 1.2.3
   assert_success 'export RBENV_VERSION="1.2.3"'
-  refute_line "return 1"
 }