graph/db: add various error assertions

Here we expand TestEdgeInsertionDeletion to assert that the expected
error is returned when AddChannelEdge is called for a channel that has
already been persisted. We also take the opportunity to convert some of
the error checks in the test to use strict error type matching.

Finally, we test that the expected error is returned if
DeleteLightningNode is called for a node that is no longer in the DB.

graph/db/graph_test.go

@@ -159,11 +159,15 @@ func TestNodeInsertionAndDeletion(t *testing.T) {
 
 	// Next, delete the node from the graph, this should purge all data
 	// related to the node.
-	if err := graph.DeleteLightningNode(testPub); err != nil {
-		t.Fatalf("unable to delete node; %v", err)
-	}
+	require.NoError(t, graph.DeleteLightningNode(testPub))
 	assertNodeNotInCache(t, graph, testPub)
 
+	// Attempting to delete the node again should return an error since
+	// the node is no longer known.
+	require.ErrorIs(
+		t, graph.DeleteLightningNode(testPub), ErrGraphNodeNotFound,
+	)
+
 	// Finally, attempt to fetch the node again. This should fail as the
 	// node should have been deleted from the database.
 	_, err = graph.FetchLightningNode(testPub)
@@ -299,6 +303,7 @@ func TestSourceNode(t *testing.T) {
 	compareNodes(t, testNode, sourceNode)
 }
 
+// TestEdgeInsertionDeletion tests the basic CRUD operations for channel edges.
 func TestEdgeInsertionDeletion(t *testing.T) {
 	t.Parallel()
 
@@ -340,40 +345,33 @@ func TestEdgeInsertionDeletion(t *testing.T) {
 	copy(edgeInfo.BitcoinKey1Bytes[:], node1Pub.SerializeCompressed())
 	copy(edgeInfo.BitcoinKey2Bytes[:], node2Pub.SerializeCompressed())
 
-	if err := graph.AddChannelEdge(&edgeInfo); err != nil {
-		t.Fatalf("unable to create channel edge: %v", err)
-	}
+	require.NoError(t, graph.AddChannelEdge(&edgeInfo))
 	assertEdgeWithNoPoliciesInCache(t, graph, &edgeInfo)
 
+	// Show that trying to insert the same channel again will return the
+	// expected error.
+	err = graph.AddChannelEdge(&edgeInfo)
+	require.ErrorIs(t, err, ErrEdgeAlreadyExist)
+
 	// Ensure that both policies are returned as unknown (nil).
 	_, e1, e2, err := graph.FetchChannelEdgesByID(chanID)
-	if err != nil {
-		t.Fatalf("unable to fetch channel edge")
-	}
-	if e1 != nil || e2 != nil {
-		t.Fatalf("channel edges not unknown")
-	}
+	require.NoError(t, err)
+	require.Nil(t, e1)
+	require.Nil(t, e2)
 
 	// Next, attempt to delete the edge from the database, again this
 	// should proceed without any issues.
-	if err := graph.DeleteChannelEdges(false, true, chanID); err != nil {
-		t.Fatalf("unable to delete edge: %v", err)
-	}
+	require.NoError(t, graph.DeleteChannelEdges(false, true, chanID))
 	assertNoEdge(t, graph, chanID)
 
 	// Ensure that any query attempts to lookup the delete channel edge are
 	// properly deleted.
 	_, _, _, err = graph.FetchChannelEdgesByOutpoint(&outpoint)
-	if err == nil {
-		t.Fatalf("channel edge not deleted")
-	}
-	if _, _, _, err := graph.FetchChannelEdgesByID(chanID); err == nil {
-		t.Fatalf("channel edge not deleted")
-	}
+	require.ErrorIs(t, err, ErrEdgeNotFound)
+	_, _, _, err = graph.FetchChannelEdgesByID(chanID)
+	require.ErrorIs(t, err, ErrZombieEdge)
 	isZombie, _, _ := graph.IsZombieEdge(chanID)
-	if !isZombie {
-		t.Fatal("channel edge not marked as zombie")
-	}
+	require.True(t, isZombie)
 
 	// Finally, attempt to delete a (now) non-existent edge within the
 	// database, this should result in an error.