[tests] Pull out common submodules

New modules: fixture, process, program, target, and thin

tests/common/program.rs

@@ -0,0 +1,43 @@
+use anyhow::Result;
+use std::ffi::OsStr;
+use std::path::PathBuf;
+
+use crate::common::test_dir::TestDir;
+
+//------------------------------------------
+
+pub enum ArgType {
+    InputArg,
+    IoOptions,
+}
+
+pub trait Program<'a> {
+    fn name() -> &'a str;
+    fn path() -> &'a OsStr;
+    fn usage() -> &'a str;
+    fn arg_type() -> ArgType;
+
+    // error messages
+    fn bad_option_hint(option: &str) -> String;
+}
+
+pub trait InputProgram<'a>: Program<'a> {
+    fn mk_valid_input(td: &mut TestDir) -> Result<PathBuf>;
+
+    // error messages
+    fn missing_input_arg() -> &'a str;
+    fn file_not_found() -> &'a str;
+    fn corrupted_input() -> &'a str;
+}
+
+pub trait BinaryInputProgram<'a>: InputProgram<'a> {}
+
+pub trait OutputProgram<'a>: InputProgram<'a> {
+    // error messages
+    fn missing_output_arg() -> &'a str;
+    fn file_not_found() -> &'a str;
+}
+
+pub trait BinaryOutputProgram<'a>: OutputProgram<'a> {}
+
+//------------------------------------------