[tests] Use traits to specify test parameters

To deal with variety in target attributes and their expected outputs,
the test parameters are categorized into traits, thus the test program
could define test parameters in a more structured way, without having
to pass multiple tightly-coupled parameters to test functions.

tests/thin_metadata_pack.rs

@@ -5,6 +5,7 @@ mod common;
 use common::common_args::*;
 use common::input_arg::*;
 use common::output_option::*;
+use common::test_dir::*;
 use common::*;
 
 //------------------------------------------
@@ -28,12 +29,66 @@ const USAGE: &str = concat!(
 
 //------------------------------------------
 
-test_accepts_help!(THIN_METADATA_PACK, USAGE);
-test_accepts_version!(THIN_METADATA_PACK);
-test_rejects_bad_option!(THIN_METADATA_PACK);
+struct ThinMetadataPack;
 
-test_missing_input_option!(THIN_METADATA_PACK);
-test_missing_output_option!(THIN_METADATA_PACK, mk_valid_md);
-test_input_file_not_found!(THIN_METADATA_PACK, OPTION);
+impl<'a> Program<'a> for ThinMetadataPack {
+    fn name() -> &'a str {
+        "thin_metadata_pack"
+    }
+
+    fn path() -> &'a str {
+        THIN_METADATA_PACK
+    }
+
+    fn usage() -> &'a str {
+        USAGE
+    }
+
+    fn arg_type() -> ArgType {
+        ArgType::IoOptions
+    }
+
+    fn bad_option_hint(option: &str) -> String {
+        rust_msg::bad_option_hint(option)
+    }
+}
+
+impl<'a> InputProgram<'a> for ThinMetadataPack {
+    fn mk_valid_input(td: &mut TestDir) -> Result<std::path::PathBuf> {
+        mk_valid_md(td)
+    }
+
+    fn file_not_found() -> &'a str {
+        rust_msg::FILE_NOT_FOUND
+    }
+
+    fn missing_input_arg() -> &'a str {
+        rust_msg::MISSING_INPUT_ARG
+    }
+
+    fn corrupted_input() -> &'a str {
+        rust_msg::BAD_SUPERBLOCK
+    }
+}
+
+impl<'a> OutputProgram<'a> for ThinMetadataPack {
+    fn file_not_found() -> &'a str {
+        rust_msg::FILE_NOT_FOUND
+    }
+
+    fn missing_output_arg() -> &'a str {
+        rust_msg::MISSING_OUTPUT_ARG
+    }
+}
 
 //------------------------------------------
+
+test_accepts_help!(ThinMetadataPack);
+test_accepts_version!(ThinMetadataPack);
+test_rejects_bad_option!(ThinMetadataPack);
+
+test_missing_input_option!(ThinMetadataPack);
+test_missing_output_option!(ThinMetadataPack);
+test_input_file_not_found!(ThinMetadataPack);
+
+//-----------------------------------------