Add test-harness fs helpers

Cargo.toml

@@ -2,6 +2,7 @@
 
 members = [
     "ghcid-ng",
+    "test-harness",
 ]
 
 resolver = "2"

test-harness/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "test-harness"
+version = "0.1.0"
+edition = "2021"
+description = "Test harness for ghcid-ng"
+publish = false
+
+[dependencies]
+miette = { version = "5.9.0", features = ["fancy"] }
+tokio = { version = "1.28.2", features = ["full", "tracing"] }

test-harness/src/fs.rs

@@ -0,0 +1,56 @@
+use std::fmt::Display;
+use std::path::Path;
+use std::time::Duration;
+
+use backoff::backoff::Backoff;
+use backoff::ExponentialBackoff;
+use miette::Context;
+use miette::IntoDiagnostic;
+use tokio::fs::File;
+use tokio::fs::OpenOptions;
+use tokio::io::AsyncWriteExt;
+
+/// Touch a path.
+pub async fn touch(path: impl AsRef<Path>) -> miette::Result<()> {
+    let path = path.as_ref();
+    OpenOptions::new()
+        .create(true)
+        .write(true)
+        .open(path)
+        .await
+        .into_diagnostic()
+        .wrap_err_with(|| format!("Failed to touch {path:?}"))
+        .map(|_| ())
+}
+
+/// Append some data to a path.
+pub async fn append(path: impl AsRef<Path>, data: impl Display) -> miette::Result<()> {
+    let path = path.as_ref();
+    let mut file = OpenOptions::new()
+        .append(true)
+        .open(path)
+        .await
+        .into_diagnostic()
+        .wrap_err_with(|| format!("Failed to open {path:?}"))?;
+    file.write_all(data.to_string().as_bytes())
+        .await
+        .into_diagnostic()?;
+    Ok(())
+}
+
+/// Wait for a path to be created.
+///
+/// This should generaly be run under a [`tokio::time::timeout`].
+pub async fn wait_for_path(path: &Path) {
+    let mut backoff = ExponentialBackoff {
+        max_interval: Duration::from_secs(1),
+        ..Default::default()
+    };
+    while let Some(duration) = backoff.next_backoff() {
+        if (File::open(path).await).is_ok() {
+            break;
+        }
+        tracing::debug!("Waiting {duration:?} before retrying");
+        tokio::time::sleep(duration).await;
+    }
+}

test-harness/src/lib.rs

@@ -0,0 +1 @@
+pub mod fs;