[tests] Pull out common submodules

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

tests/common/fixture.rs

@@ -0,0 +1,69 @@
+use anyhow::Result;
+use std::fs::OpenOptions;
+use std::io::{Read, Write};
+use std::path::PathBuf;
+
+use thinp::file_utils;
+
+use crate::common::test_dir::TestDir;
+
+//------------------------------------------
+
+pub fn mk_zeroed_md(td: &mut TestDir) -> Result<PathBuf> {
+    let md = td.mk_path("meta.bin");
+    eprintln!("path = {:?}", md);
+    let _file = file_utils::create_sized_file(&md, 1024 * 1024 * 16);
+    Ok(md)
+}
+
+pub fn damage_superblock(path: &PathBuf) -> Result<()> {
+    let mut output = OpenOptions::new().read(false).write(true).open(path)?;
+    let buf = [0u8; 512];
+    output.write_all(&buf)?;
+    Ok(())
+}
+
+//------------------------------------------
+
+pub fn md5(md: &PathBuf) -> Result<String> {
+    let output = duct::cmd!("md5sum", "-b", &md).stdout_capture().run()?;
+    let csum = std::str::from_utf8(&output.stdout[0..])?.to_string();
+    let csum = csum.split_ascii_whitespace().next().unwrap().to_string();
+    Ok(csum)
+}
+
+// This checksums the file before and after the thunk is run to
+// ensure it is unchanged.
+pub fn ensure_untouched<F>(p: &PathBuf, thunk: F) -> Result<()>
+where
+    F: Fn() -> Result<()>,
+{
+    let csum = md5(p)?;
+    thunk()?;
+    assert_eq!(csum, md5(p)?);
+    Ok(())
+}
+
+pub fn superblock_all_zeroes(path: &PathBuf) -> Result<bool> {
+    let mut input = OpenOptions::new().read(true).write(false).open(path)?;
+    let mut buf = vec![0; 4096];
+    input.read_exact(&mut buf[0..])?;
+    for b in buf {
+        if b != 0 {
+            return Ok(false);
+        }
+    }
+
+    Ok(true)
+}
+
+pub fn ensure_superblock_zeroed<F>(p: &PathBuf, thunk: F) -> Result<()>
+where
+    F: Fn() -> Result<()>,
+{
+    thunk()?;
+    assert!(superblock_all_zeroes(p)?);
+    Ok(())
+}
+
+//------------------------------------------