tests/printenv: add more tests (uutils#9151)

* tests/printenv: add more tests

* tests/printenv: use clearer checks in tests

Author: ya7on

tests/by-util/test_printenv.rs

@@ -18,9 +18,10 @@ fn test_get_all() {
 fn test_get_var() {
     new_ucmd!()
         .env("KEY", "VALUE")
+        .env("FOO", "BAR")
         .arg("KEY")
         .succeeds()
-        .stdout_contains("VALUE\n");
+        .stdout_is("VALUE\n");
 }
 
 #[test]
@@ -29,6 +30,31 @@ fn test_ignore_equal_var() {
     new_ucmd!().env("a=b", "c").arg("a=b").fails().no_stdout();
 }
 
+#[test]
+fn test_silent_error_equal_var() {
+    // printenv should ignore variables with equal signs e.g. a=b=c
+    new_ucmd!()
+        .env("KEY", "VALUE")
+        .env("a=b", "c")
+        .arg("KEY")
+        .arg("a=b")
+        .fails_with_code(1)
+        .stdout_is("VALUE\n")
+        .no_stderr();
+}
+
+#[test]
+fn test_silent_error_not_present() {
+    // printenv should ignore unspecified variables, not panic on them
+    new_ucmd!()
+        .env("KEY", "VALUE")
+        .arg("FOO")
+        .arg("KEY")
+        .fails_with_code(1)
+        .stdout_is("VALUE\n")
+        .no_stderr();
+}
+
 #[test]
 fn test_invalid_option_exit_code() {
     // printenv should return exit code 2 for invalid options
@@ -40,3 +66,27 @@ fn test_invalid_option_exit_code() {
         .stderr_contains("unexpected argument")
         .stderr_contains("For more information, try '--help'");
 }
+
+#[test]
+fn test_null_separator() {
+    // printenv should use \x00 as separator if null option is provided
+    for null_opt in ["-0", "--null"] {
+        new_ucmd!()
+            .env("HOME", "FOO")
+            .env("KEY", "VALUE")
+            .arg(null_opt)
+            .succeeds()
+            .stdout_contains("HOME=FOO\x00")
+            .stdout_contains("KEY=VALUE\x00");
+
+        new_ucmd!()
+            .env("HOME", "FOO")
+            .env("KEY", "VALUE")
+            .env("FOO", "BAR")
+            .arg(null_opt)
+            .arg("HOME")
+            .arg("KEY")
+            .succeeds()
+            .stdout_is("FOO\x00VALUE\x00");
+    }
+}