anchor.diff:            startedAt: startedAt,
           );
   
  -        whenDocumentSnapshotData().thenReturn(DocumentData.fromMap(buildJson));
  -
  -        await onBuildAddedHandler(documentSnapshotMock, null);
  +        whenDocument().thenReturn(documentReference);
  +        when(documentSnapshot.data).thenReturn(
  +          DocumentData.fromMap(buildJson),
  +        );
  +
  +        await onBuildAddedHandler(documentSnapshot, null);
   
           final documentId =
               '${projectId}_${startedAtDayUtc.millisecondsSinceEpoch}';
   
  -        verify(firestoreMock.document('build_days/$documentId')).called(1);
  +        verify(firestore.document('build_days/$documentId')).called(1);
         },
       );
   
  
positive.code:         );
          final expectedDate = startedAtDayUtc.millisecondsSinceEpoch;
  
          whenDocumentSnapshotData().thenReturn(DocumentData.fromMap(buildJson));
  
          await onBuildAddedHandler(documentSnapshotMock, null);
  
          expect(
            verify(firestoreMock.document(captureAny)).captured.single,
            contains(expectedDate.toString()),
          );
        },
  
negative.code:     test(
        "creates a build days document with project id equals to the build document snapshot's project id",
        () async {
          whenDocument().thenReturn(documentReference);
          when(documentSnapshot.data).thenReturn(buildDocumentData);
  
          await onBuildAddedHandler(documentSnapshot, null);
  
          final projectIdMatcher = predicate<DocumentData>(
            (data) => data.getString('projectId') == projectId,
          );
  
          verify(
            documentReference.setData(
              argThat(projectIdMatcher),
              any,
            ),
  