test: remove committed .png files and generate into temp dir

There's not much point in committing them (and having to keep them up to date
would be unnecessary hassle). The rendering is done with resvg anyway.

Author: not-my-profile

Cargo.lock

@@ -55,6 +55,7 @@ regex = "1.12.2"
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 assert_cmd = "2.1.1"
 libtest-mimic = "0.8.1"
+tempfile = "3"
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3"

Cargo.toml

@@ -7,6 +7,8 @@ use std::path::PathBuf;
 use assert_cmd::cargo::cargo_bin_cmd;
 #[cfg(not(target_arch = "wasm32"))]
 use libtest_mimic::Failed;
+#[cfg(not(target_arch = "wasm32"))]
+use tempfile::TempDir;
 
 #[cfg(target_arch = "wasm32")]
 fn main() {}
@@ -48,10 +50,7 @@ fn main() {
                 }),
                 libtest_mimic::Trial::test(format!("png_{stem}"), {
                     let in_path = in_path.clone();
-                    let out_path = manifest_dir
-                        .join("tests/output/png")
-                        .join(format!("{stem}.png"));
-                    move || smoke_test_png(in_path, out_path)
+                    move || smoke_test_png(in_path)
                 }),
             ]
         })
@@ -87,14 +86,15 @@ fn smoke_test_svg(in_path: PathBuf, out_path: PathBuf) -> Result<(), Failed> {
 }
 
 #[cfg(not(target_arch = "wasm32"))]
-fn smoke_test_png(in_path: PathBuf, out_path: PathBuf) -> Result<(), Failed> {
-    if out_path.exists() {
-        fs::remove_file(&out_path)?;
-    }
+fn smoke_test_png(in_path: PathBuf) -> Result<(), Failed> {
+    let temp_dir = TempDir::new().expect("create temp dir");
+
+    let stem = in_path.file_stem().unwrap().to_str().unwrap();
+    let out_path = temp_dir.path().join(format!("{stem}.png"));
 
     let mut cmd = cargo_bin_cmd!("oxdraw");
     cmd.arg("--input")
-        .arg(in_path)
+        .arg(&in_path)
         .arg("--output")
         .arg(&out_path)
         .arg("--output-format")
@@ -103,10 +103,13 @@ fn smoke_test_png(in_path: PathBuf, out_path: PathBuf) -> Result<(), Failed> {
     cmd.assert().success();
 
     let png_bytes = fs::read(&out_path)?;
-    assert!(
-        png_bytes.starts_with(b"\x89PNG\r\n\x1a\n"),
-        "{} output should begin with the PNG magic header",
-        out_path.display()
-    );
+    let starts_with_header = png_bytes.starts_with(b"\x89PNG\r\n\x1a\n");
+    if !starts_with_header {
+        let _ = temp_dir.keep();
+        panic!(
+            "{} output should begin with the PNG magic header",
+            out_path.display()
+        );
+    }
     Ok(())
 }