diff --git a/cmd/html2article/conv.go b/cmd/html2article/conv.go
index d9d5e9d9..d3267d7a 100644
--- a/cmd/html2article/conv.go
+++ b/cmd/html2article/conv.go
@@ -223,7 +223,7 @@ func text(n *html.Node) string {
 			}
 			// Use original url for Google Docs redirections.
 			if u, err := url.Parse(href); err != nil {
-				log.Println("parsing url %q: %v", href, err)
+				log.Printf("parsing url %q: %v", href, err)
 			} else if u.Host == "www.google.com" && u.Path == "/url" {
 				href = u.Query().Get("q")
 			}
diff --git a/container/intsets/sparse_test.go b/container/intsets/sparse_test.go
index 23382019..ec303d91 100644
--- a/container/intsets/sparse_test.go
+++ b/container/intsets/sparse_test.go
@@ -60,7 +60,7 @@ func TestBasics(t *testing.T) {
 
 // Insert, Len, IsEmpty, Hash, Clear, AppendTo.
 func TestMoreBasics(t *testing.T) {
-	var set intsets.Sparse
+	set := new(intsets.Sparse)
 	set.Insert(456)
 	set.Insert(123)
 	set.Insert(789)
@@ -78,7 +78,7 @@ func TestMoreBasics(t *testing.T) {
 	}
 	got := set.AppendTo([]int{-1})
 	if want := []int{-1, 123, 456, 789}; fmt.Sprint(got) != fmt.Sprint(want) {
-		t.Errorf("%s.AppendTo: got %v, want %v", got, want)
+		t.Errorf("%s.AppendTo: got %v, want %v", set, got, want)
 	}
 
 	set.Clear()
@@ -107,7 +107,7 @@ func TestTakeMin(t *testing.T) {
 		}
 	}
 	if set.TakeMin(&got) {
-		t.Errorf("%s.TakeMin returned true", set, got)
+		t.Errorf("%s.TakeMin returned true", &set)
 	}
 	if err := set.Check(); err != nil {
 		t.Fatalf("check: %s: %#v", err, &set)
diff --git a/dashboard/builder/bench.go b/dashboard/builder/bench.go
index fb99aac5..a9a59ce3 100644
--- a/dashboard/builder/bench.go
+++ b/dashboard/builder/bench.go
@@ -118,7 +118,7 @@ func chooseBenchmark(benchBin string, doneBenchs []string) (bench string, procs,
 	var out bytes.Buffer
 	err := run(exec.Command(benchBin), allOutput(&out))
 	if err != nil {
-		log.Printf("Failed to query benchmark list: %v\n%s", err, out)
+		log.Printf("Failed to query benchmark list: %v\n%s", err, &out)
 		last = true
 		return
 	}
diff --git a/go/loader/loader_test.go b/go/loader/loader_test.go
index c239c632..95868a88 100644
--- a/go/loader/loader_test.go
+++ b/go/loader/loader_test.go
@@ -106,7 +106,7 @@ func TestLoadFromArgsSource(t *testing.T) {
 		t.Fatalf("loadFromArgs(%q) failed: %s", args, err)
 	}
 	if len(prog.Created) != 1 {
-		t.Errorf("loadFromArgs(%q): got %d items, want 1", len(prog.Created))
+		t.Errorf("loadFromArgs(%q): got %d items, want 1", args, len(prog.Created))
 	}
 	if len(prog.Created) > 0 {
 		path := prog.Created[0].Pkg.Path()
diff --git a/go/types/api_test.go b/go/types/api_test.go
index ad3d30b8..57f7edc7 100644
--- a/go/types/api_test.go
+++ b/go/types/api_test.go
@@ -813,10 +813,10 @@ func main() {
 			got := sig.Recv().Type()
 			want := sel.Recv()
 			if !Identical(got, want) {
-				t.Errorf("%s: Recv() = %s, want %s", got, want)
+				t.Errorf("%s: Recv() = %s, want %s", syntax, got, want)
 			}
 		} else if sig != nil && sig.Recv() != nil {
-			t.Error("%s: signature has receiver %s", sig, sig.Recv().Type())
+			t.Errorf("%s: signature has receiver %s", sig, sig.Recv().Type())
 		}
 	}
 	// Assert that all wantOut entries were used exactly once.