                                         let relation = relation._including(all: association)
                                         do {
                                             XCTAssertEqual(relation.children.count, 1)
-                                            // TODO: what is the purpose of the name of the `.bridge` children, from the point of view of the user?
-                                            //                                                           ~~~~~~~~~~~~~~~~~~~~~~~
                                             XCTAssertEqual(relation.children[0].key, key1.name(singular: cardinality1.isSingular))
                                             XCTAssertEqual(relation.children[0].value.kind, .bridge)
                                             XCTAssertEqual(relation.children[0].value.relation.children.count, 1)
-                                            // TODO: what is the purpose of the name of the `.bridge` children, from the point of view of the user?
-                                            //                                                                                      ~~~~~~~~~~~~~~~~~~~~~~~
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].key, key2.name(singular: cardinality2.isSingular))
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].value.kind, .bridge)
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].value.relation.children.count, 1)
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].value.relation.children[0].key, key3.name(singular: false))
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].value.relation.children[0].value.kind, .all)
                                         }
-                                        #warning("TODO: here we see the problem: it should be possible to merge association1 when it is singular.")
-                                        // TODO: what is the purpose of the name of the `.bridge` children, from the point of view of the user?
-                                        // ~~~~~~~~~~~~~~~~~~~~~~~~
+                                        // TODO: here we see the problem: it should be possible to merge association1 when it is singular.
                                         if !cardinality1.isSingular && key1.name(singular: true) != key1.name(singular: false) {
                                             let relation = relation._joining(optional: association1)
                                             XCTAssertEqual(relation.children.count, 2)
-                                            // TODO: what is the purpose of the name of the `.bridge` children, from the point of view of the user?
-                                            //                                                           ~~~~~~~~~~~~~~~~~~~~~~~
                                             XCTAssertEqual(relation.children[0].key, key1.name(singular: cardinality1.isSingular))
                                             XCTAssertEqual(relation.children[0].value.kind, .bridge)
                                             XCTAssertEqual(relation.children[0].value.relation.children.count, 1)
-                                            // TODO: what is the purpose of the name of the `.bridge` children, from the point of view of the user?
-                                            //                                                                                      ~~~~~~~~~~~~~~~~~~~~~~~
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].key, key2.name(singular: cardinality2.isSingular))
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].value.kind, .bridge)
                                             XCTAssertEqual(relation.children[0].value.relation.children[0].value.relation.children.count, 1)

                            let relation = relation._including(all: association)
                            do {
                                XCTAssertEqual(relation.children.count, 1)
                                // TODO: what is the purpose of the name of the `.bridge` children, from the point of view of the user?
                                //                                                           ~~~~~~~~~~~~~~~~~~~~~~~
                                XCTAssertEqual(relation.children[0].key, key1.name(singular: cardinality1.isSingular))
                                XCTAssertEqual(relation.children[0].value.kind, .bridge)
                                XCTAssertEqual(relation.children[0].value.relation.children.count, 1)

                                    XCTAssertEqual(relation.children[0].value.relation.children[0].key, key2.name(singular: true))
                                    XCTAssertEqual(relation.children[0].value.relation.children[0].value.kind, .oneRequired)
                                }
                                if !cardinality1.isSingular && key1.name(singular: true) != key1.name(singular: false) {
                                    let relation = relation._including(all: association)
                                    XCTAssertEqual(relation.children.count, 2)
