From 1fef80d659921d77770949418cd38eb7a1d7366c Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Sun, 30 Sep 2018 07:32:24 -0400
Subject: [PATCH] expand incremental tests

---
 src/runtime.rs               |  2 +-
 tests/incremental/queries.rs |  2 +-
 tests/incremental/tests.rs   | 26 +++++++++++++++++++++++++-
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/runtime.rs b/src/runtime.rs
index abdaf65c..4e6fbd4e 100644
--- a/src/runtime.rs
+++ b/src/runtime.rs
@@ -202,7 +202,7 @@ impl Revision {
 
 impl std::fmt::Debug for Revision {
     fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(fmt, "R({})", self.generation)
+        write!(fmt, "R{}", self.generation)
     }
 }
 
diff --git a/tests/incremental/queries.rs b/tests/incremental/queries.rs
index 65ac9d69..328adfbd 100644
--- a/tests/incremental/queries.rs
+++ b/tests/incremental/queries.rs
@@ -25,7 +25,7 @@ salsa::query_definition! {
     crate Memoized1(query: &impl QueryContext, (): ()) -> usize {
         query.log().add("Memoized1 invoked");
         let v = query.volatile().of(());
-        v / 3
+        v / 2
     }
 }
 
diff --git a/tests/incremental/tests.rs b/tests/incremental/tests.rs
index ac516ad5..f4cbacb6 100644
--- a/tests/incremental/tests.rs
+++ b/tests/incremental/tests.rs
@@ -40,8 +40,16 @@ fn volatile_x2() {
     query.assert_log(&["Volatile invoked", "Volatile invoked"]);
 }
 
+/// Test that:
+///
+/// - On the first run of R0, we recompute everything.
+/// - On the second run of R1, we recompute nothing.
+/// - On the first run of R1, we recompute Memoized1 but not Memoized2 (since Memoized1 result
+///   did not change).
+/// - On the second run of R1, we recompute nothing.
+/// - On the first run of R2, we recompute everything (since Memoized1 result *did* change).
 #[test]
-fn foo() {
+fn revalidate() {
     env_logger::init();
 
     let query = QueryContextImpl::default();
@@ -52,8 +60,24 @@ fn foo() {
     query.memoized2().of(());
     query.assert_log(&[]);
 
+    // Second generation: volatile will change (to 1) but memoized1
+    // will not (still 0, as 1/2 = 0)
     query.salsa_runtime().next_revision();
 
     query.memoized2().of(());
     query.assert_log(&["Memoized1 invoked", "Volatile invoked"]);
+
+    query.memoized2().of(());
+    query.assert_log(&[]);
+
+    // Third generation: volatile will change (to 2) and memoized1
+    // will too (to 1).  Therefore, after validating that Memoized1
+    // changed, we now invoke Memoized2.
+    query.salsa_runtime().next_revision();
+
+    query.memoized2().of(());
+    query.assert_log(&["Memoized1 invoked", "Volatile invoked", "Memoized2 invoked"]);
+
+    query.memoized2().of(());
+    query.assert_log(&[]);
 }