improve test for validation execution order

The test wanted to verify that in a file containing
  build foo: ... |@ bar
it's possible for foo to finish before bar does.

This changes to the test to make the bar step wait (at runtime) for the
foo step to finish, enforcing that that ordering is possible.

Fixes #102.

2 files changed, 12 insertions, 29 deletions

diff --git a/tests/e2e/mod.rs b/tests/e2e/mod.rs
index 93f26ff..a1e7e7f 100644
--- a/tests/e2e/mod.rs
+++ b/tests/e2e/mod.rs
@@ -84,10 +84,6 @@ impl TestSpace {
         Ok(())
     }
 
-    pub fn path(&self) -> &std::path::Path {
-        self.dir.path()
-    }
-
     /// Invoke n2, returning process output.
     pub fn run(&self, cmd: &mut std::process::Command) -> std::io::Result<std::process::Output> {
         cmd.current_dir(self.dir.path()).output()
diff --git a/tests/e2e/validations.rs b/tests/e2e/validations.rs
index 1b1eb98..46c48ae 100644
--- a/tests/e2e/validations.rs
+++ b/tests/e2e/validations.rs
@@ -1,3 +1,5 @@
+//! Tests for the 'validations' feature, which are build edges marked with |@.
+
 use crate::e2e::*;
 
 #[test]
@@ -22,44 +24,29 @@ fn basic_validation() -> anyhow::Result<()> {
 #[cfg(unix)]
 #[test]
 fn build_starts_before_validation_finishes() -> anyhow::Result<()> {
+    // When a given target has a validation, that validation is part of the
+    // overall build.  But despite there being a build edge, the target shouldn't
+    // wait for the validation.
+    // To verify this, we make the validation command internally wait for the
+    // target, effectively reversing the dependency order at runtime.
     let space = TestSpace::new()?;
     space.write(
         "build.ninja",
         "
+# Waits for the file $wait_for to exist, then touches $out.
 rule build_slow
-  command = sleep 0.3 && touch $out
+  command = until [ -f $wait_for ]; do sleep 0.1; done; touch $out
 
 rule build_fast
-  command = sleep 0.1 && touch $out
+  command = touch $out
 
 build out: build_fast regular_input |@ validation_input
 build regular_input: build_fast
 build validation_input: build_slow
+  wait_for = regular_input
 ",
     )?;
-    let command = n2_command(vec!["out"])
-        .current_dir(space.path())
-        .stdout(std::process::Stdio::null())
-        .stderr(std::process::Stdio::null())
-        .stdin(std::process::Stdio::null())
-        .spawn()?;
-    std::thread::sleep(std::time::Duration::from_millis(50));
-    assert!(space.read("out").is_err());
-    assert!(space.read("regular_input").is_err());
-    assert!(space.read("validation_input").is_err());
-    std::thread::sleep(std::time::Duration::from_millis(100));
-    assert!(space.read("out").is_err());
-    assert!(space.read("regular_input").is_ok());
-    assert!(space.read("validation_input").is_err());
-    std::thread::sleep(std::time::Duration::from_millis(100));
-    assert!(space.read("out").is_ok());
-    assert!(space.read("regular_input").is_ok());
-    assert!(space.read("validation_input").is_err());
-    std::thread::sleep(std::time::Duration::from_millis(100));
-    assert!(space.read("out").is_ok());
-    assert!(space.read("regular_input").is_ok());
-    assert!(space.read("validation_input").is_ok());
-    assert!(command.wait_with_output()?.status.success());
+    space.run_expect(&mut n2_command(vec!["out"]))?;
     Ok(())
 }