Add build scheduler DB interface, dumb in-memory impl, cache

build_scheduler/go/db/cache_test.go

Index: build_scheduler/go/db/cache_test.go
diff --git a/build_scheduler/go/db/cache_test.go b/build_scheduler/go/db/cache_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..e86cd601cf8f8897dc5f337b4309c10b5489bb39
--- /dev/null
+++ b/build_scheduler/go/db/cache_test.go
@@ -0,0 +1,60 @@
+package db
+
+import (
+	"testing"
+	"time"
+
+	assert "github.com/stretchr/testify/require"
+	"go.skia.org/infra/go/testutils"
+)
+
+func testGetBuildsForCommits(t *testing.T, c *BuildCache, b *Build) {
+	for _, commit := range b.Commits {
+		builds, err := c.GetBuildsForCommits([]string{commit})
+		assert.NoError(t, err)
+		testutils.AssertDeepEqual(t, map[string]map[string]*Build{
+			commit: map[string]*Build{
+				b.Builder: b,
+			},
+		}, builds)
+	}
+}
+
+func TestDBCache(t *testing.T) {
+	db := NewInMemoryDB()
+	defer testutils.AssertCloses(t, db)
+
+	// Pre-load a build into the DB.
+	startTime := time.Now().Add(-30 * time.Minute) // Arbitrary starting point.
+	b1 := makeBuild("build1", startTime, []string{"a", "b", "c", "d"})
+	assert.NoError(t, db.PutBuild(b1))
+
+	// Create the cache. Ensure that the existing build is present.
+	c, err := NewBuildCache(db, time.Hour)
+	assert.NoError(t, err)
+	testGetBuildsForCommits(t, c, b1)
+
+	// Bisect the first build.
+	b2 := makeBuild("build2", startTime.Add(time.Minute), []string{"c", "d"})
+	b1.Commits = []string{"a", "b"}
+	assert.NoError(t, db.PutBuilds([]*Build{b2, b1}))
+	assert.NoError(t, c.Update())
+
+	// Ensure that b2 (and not b1) shows up for commits "c" and "d".
+	testGetBuildsForCommits(t, c, b1)
+	testGetBuildsForCommits(t, c, b2)
+
+	// Insert a build on a second bot.
+	b3 := makeBuild("build3", startTime.Add(2*time.Minute), []string{"a", "b"})
+	b3.Builder = "Another-Builder"
+	assert.NoError(t, db.PutBuild(b3))
+	assert.NoError(t, c.Update())
+	builds, err := c.GetBuildsForCommits([]string{"b"})
+	assert.NoError(t, err)
+	testutils.AssertDeepEqual(t, map[string]map[string]*Build{
+		"b": map[string]*Build{
+			b1.Builder: b1,
+			b3.Builder: b3,
+		},
+	}, builds)
+}