How to test IO code in JUnit?
- by add
I'm want to test two services:
service which builds file name
service which writes some data into file provided by 1st service
In first i'm building some complex file structure (just for example {user}/{date}/{time}/{generatedId}.bin)
In second i'm writing data to the file passed by first service (1st service calls 2nd service)
How can I test both services using mocks without making any real IO interractions?
Just for example:
1st service:
public class DefaultLogService implements LogService
{
public void log(SomeComplexData data)
{
serializer.write(new FileOutputStream(buildComplexFileStructure()), data);
or
serializer.write(buildComplexFileStructure(), data);
or
serializer.write(new GenericInputEntity(buildComplexFileStructure()), data);
}
private ComplextDataSerializer serializer; // mocked in tests
}
2nd service:
public class DefaultComplexDataSerializer implements ComplexDataSerializer
{
void write(InputStream stream, SomeComplexData data) {...}
or
void write(File file, SomeCompexData data) {...}
or
void write(GenericInputEntity entity, SomeComplexData data) {...}
}
In first case i need to pass FileOutputStream which will create a file (i.e. i can't test 1st service)
In second case i need to pass File. What can i do in 2nd service test if I need to test data which will be written to specified file? (i can't test 2nd service)
In third case i think i need some generic IO object which will wrap File.
Maybe there is some ready-to-use solution for this purpose?
