sq: add scaffolding for an integration/acceptance test suite

Add support for an integration and acceptance test suite using the
Subplot tool (https://subplot.liw.fi/). There are the initial, very
simple test scenarios, to get us started. The goal is to introduce the
scaffolding for integration tests, so that further tests can be added
with ease later.

The tests are documented and defined in sq-subplot.md. In build.rs, we
call Subplot to generate test code from the markdown file. The tests
are run via "cargo test", as usual.

Subplot can also generate a typeset test document from sq-subplot.md,
but we don't do that here.

2 files changed, 38 insertions, 0 deletions

diff --git a/sq/subplot/sq-subplot.rs b/sq/subplot/sq-subplot.rs
new file mode 100644
index 00000000..dba22e9e
--- /dev/null
+++ b/sq/subplot/sq-subplot.rs
@@ -0,0 +1,34 @@
+// Rust support for running sq-subplot.md scenarios.
+
+use subplotlib::steplibrary::runcmd::Runcmd;
+
+use std::path::Path;
+
+#[step]
+#[context(Runcmd)]
+fn install_sq(context: &ScenarioContext) {
+    // The SQ_DIR variable can be set to test an installed sq rather
+    // than the one built from the source tree.
+    if let Some(bindir) = std::env::var_os("SQ_DIR") {
+        println!("Found SQ_DIR environment variable, using that");
+        context.with_mut(
+            |rc: &mut Runcmd| {
+                rc.prepend_to_path(bindir);
+                Ok(())
+            },
+            false,
+        )?;
+    } else {
+        let target_exe = env!("CARGO_BIN_EXE_sq");
+        let target_path = Path::new(target_exe);
+        let target_path = target_path.parent().ok_or("No parent?")?;
+
+        context.with_mut(
+            |context: &mut Runcmd| {
+                context.prepend_to_path(target_path);
+                Ok(())
+            },
+            false,
+        )?;
+    }
+}
diff --git a/sq/subplot/sq-subplot.yaml b/sq/subplot/sq-subplot.yaml
new file mode 100644
index 00000000..084d7e2e
--- /dev/null
+++ b/sq/subplot/sq-subplot.yaml
@@ -0,0 +1,4 @@
+- given: "an installed sq"
+  impl:
+    rust:
+      function: install_sq