tests: add `test-incremental` step

This is contained in the `test` step, so is tested by CI.

This commit also includes some enhancements to the `incr-check` tool to
make this work correctly.

1 files changed, 28 insertions, 0 deletions

diff --git a/test/tests.zig b/test/tests.zig
index 1e98a48489..017f9478a9 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -1509,3 +1509,31 @@ pub fn addDebuggerTests(b: *std.Build, options: DebuggerContext.Options) ?*Step
     });
     return step;
 }
+
+pub fn addIncrementalTests(b: *std.Build, test_step: *Step) !void {
+    const incr_check = b.addExecutable(.{
+        .name = "incr-check",
+        .root_source_file = b.path("tools/incr-check.zig"),
+        .target = b.graph.host,
+        .optimize = .Debug,
+    });
+
+    var dir = try b.build_root.handle.openDir("test/incremental", .{ .iterate = true });
+    defer dir.close();
+
+    var it = try dir.walk(b.graph.arena);
+    while (try it.next()) |entry| {
+        if (entry.kind != .file) continue;
+
+        const run = b.addRunArtifact(incr_check);
+        run.setName(b.fmt("incr-check '{s}'", .{entry.basename}));
+
+        run.addArg(b.graph.zig_exe);
+        run.addFileArg(b.path("test/incremental/").path(b, entry.path));
+        run.addArgs(&.{ "--zig-lib-dir", b.fmt("{}", .{b.graph.zig_lib_directory}) });
+
+        run.addCheck(.{ .expect_term = .{ .Exited = 0 } });
+
+        test_step.dependOn(&run.step);
+    }
+}