1 files changed, 40 insertions, 0 deletions
diff --git a/types/stitem_test.go b/types/stitem_test.go
new file mode 100644
index 0000000..c6e413a
--- /dev/null
+++ b/types/stitem_test.go
@@ -0,0 +1,40 @@
+package types
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestStItemString checks that the String() function prints the right format,
+// and that the body is printed without a nil-pointer panic.
+func TestStItemString(t *testing.T) {
+	wantPrefix := map[StFormat]string{
+		StFormatReserved:           "Format(reserved)",
+		StFormatSignedTreeHeadV1:   "Format(signed_tree_head_v1): &{TreeHead",
+		StFormatCosignedTreeHeadV1: "Format(cosigned_tree_head_v1): &{SignedTreeHead",
+		StFormatConsistencyProofV1: "Format(consistency_proof_v1): &{LogId",
+		StFormatInclusionProofV1:   "Format(inclusion_proof_v1): &{LogId",
+		StFormatSignedChecksumV1:   "Format(signed_checksum_v1): &{Data",
+		StFormat(1<<16 - 1):        "unknown StItem: unknown StFormat: 65535",
+	}
+	tests := append(test_cases_stitem(t), testCaseSerialize{
+		description: "valid: unknown StItem",
+		item: StItem{
+			Format: StFormat(1<<16 - 1),
+		},
+	})
+	for _, table := range tests {
+		item, ok := table.item.(StItem)
+		if !ok {
+			t.Fatalf("must cast to StItem in test %q", table.description)
+		}
+
+		prefix, ok := wantPrefix[item.Format]
+		if !ok {
+			t.Fatalf("must have prefix for StFormat %v in test %q", item.Format, table.description)
+		}
+		if got, want := item.String(), prefix; !strings.HasPrefix(got, want) {
+			t.Errorf("got %q but wanted prefix %q in test %q", got, want, table.description)
+		}
+	}
+}