Exercise code path when --prompt and clevis specified

Run a test to cover the error return when --prompt and
--unlock-method=clevis are specified.

Signed-off-by: mulhern <[email protected]>

tests/stratis_min.rs

@@ -163,6 +163,23 @@ fn test_stratis_min_create_no_blockdevs() {
         ));
 }
 
+#[test]
+// Test starting a pool using both a prompt and an unlock method of clevis.
+fn test_stratis_min_pool_start_invalid_arg_combination() {
+    let mut cmd = Command::cargo_bin("stratis-min").unwrap();
+    cmd.arg("pool")
+        .arg("start")
+        .arg("--name")
+        .arg("pn")
+        .arg("--unlock-method")
+        .arg("clevis")
+        .arg("--prompt");
+    cmd.assert()
+        .failure()
+        .code(1)
+        .stderr(predicate::str::contains("mutually exclusive"));
+}
+
 #[test]
 // Test stopping a pool using an invalid UUID; unless name is specified the
 // id value is interpreted as a UUID.