Add more tests for MongoDB state store component (#948)

state/mongodb/mongodb.go

@@ -338,6 +338,10 @@ func getMongoDBMetaData(metadata state.Metadata) (*mongoDBMetadata, error) {
 		return nil, errors.New("must set 'host' or 'server' fields in metadata")
 	}
 
+	if len(meta.host) != 0 && len(meta.server) != 0 {
+		return nil, errors.New("'host' or 'server' fields are mutually exclusive")
+	}
+
 	if val, ok := metadata.Properties[username]; ok && val != "" {
 		meta.username = val
 	}

state/mongodb/mongodb_test.go

@@ -126,9 +126,9 @@ func TestGetMongoDBMetadata(t *testing.T) {
 
 	t.Run("Valid connectionstring with DNS SRV", func(t *testing.T) {
 		properties := map[string]string{
+			server:         "server.example.com",
 			databaseName:   "TestDB",
 			collectionName: "TestCollection",
-			server:         "server.example.com",
 			params:         "?ssl=true",
 		}
 		m := state.Metadata{
@@ -143,4 +143,38 @@ func TestGetMongoDBMetadata(t *testing.T) {
 
 		assert.Equal(t, expected, uri)
 	})
+
+	t.Run("Invalid without host/server", func(t *testing.T) {
+		properties := map[string]string{
+			databaseName:   "TestDB",
+			collectionName: "TestCollection",
+		}
+		m := state.Metadata{
+			Properties: properties,
+		}
+
+		_, err := getMongoDBMetaData(m)
+		assert.NotNil(t, err)
+
+		expected := "must set 'host' or 'server' fields in metadata"
+		assert.Equal(t, expected, err.Error())
+	})
+
+	t.Run("Invalid with both host/server", func(t *testing.T) {
+		properties := map[string]string{
+			server:         "server.example.com",
+			host:           "127.0.0.2",
+			databaseName:   "TestDB",
+			collectionName: "TestCollection",
+		}
+		m := state.Metadata{
+			Properties: properties,
+		}
+
+		_, err := getMongoDBMetaData(m)
+		assert.NotNil(t, err)
+
+		expected := "'host' or 'server' fields are mutually exclusive"
+		assert.Equal(t, expected, err.Error())
+	})
 }