Fix breaking changes in Render contract

[DrSatyr]

#741 fix

[PawelWesolowski]

it should return on the stream not the writer - sth like: return byteArrayOutputStream.toString();
not
return outputStreamWriter.toString();

I can fix and add a test.

[DrSatyr]

@PawelWesolowski you're absolutely right regarding the issue. I just left the testing to the evening, cause had no time.

[PawelWesolowski]

Looks awesome.
How about adding a test which is doing exactly what's in the docs? Sth like:

  @Test
  public void testDiffAndJsonWithoutProvidingStream() {
    ChangedOpenApi diff = OpenApiCompare.fromLocations(OPENAPI_DOC1, OPENAPI_DOC2);
    Render render = new JsonRender();
    String renderedAsString = render.render(diff);
    assertThat(renderedAsString).contains("\"newEndpoints\":");
  }

at OpenApiDiffTest.java

[DrSatyr]

Looks awesome. How about adding a test which is doing exactly what's in the docs? Sth like:

  @Test
  public void testDiffAndJsonWithoutProvidingStream() {
    ChangedOpenApi diff = OpenApiCompare.fromLocations(OPENAPI_DOC1, OPENAPI_DOC2);
    Render render = new JsonRender();
    String renderedAsString = render.render(diff);
    assertThat(renderedAsString).contains("\"newEndpoints\":");
  }

at OpenApiDiffTest.java

Each render has its own test class (eg JsonRenderTest), and they are doing pretty much the same as in doc (I've updated Readme to conform to the new approach, the old one is deprecated and can lead to issues)

[PawelWesolowski]

Looks awesome. How about adding a test which is doing exactly what's in the docs? Sth like:

  @Test
  public void testDiffAndJsonWithoutProvidingStream() {
    ChangedOpenApi diff = OpenApiCompare.fromLocations(OPENAPI_DOC1, OPENAPI_DOC2);
    Render render = new JsonRender();
    String renderedAsString = render.render(diff);
    assertThat(renderedAsString).contains("\"newEndpoints\":");
  }

at OpenApiDiffTest.java

Each render has its own test class (eg JsonRenderTest), and they are doing pretty much the same as in doc.

None of them failed after the first commit on this fix. The one I suggested did.

[DrSatyr]

Looks awesome. How about adding a test which is doing exactly what's in the docs? Sth like:

  @Test
  public void testDiffAndJsonWithoutProvidingStream() {
    ChangedOpenApi diff = OpenApiCompare.fromLocations(OPENAPI_DOC1, OPENAPI_DOC2);
    Render render = new JsonRender();
    String renderedAsString = render.render(diff);
    assertThat(renderedAsString).contains("\"newEndpoints\":");
  }

at OpenApiDiffTest.java

Each render has its own test class (eg JsonRenderTest), and they are doing pretty much the same as in doc.

None of them failed after the first commit on this fix. The one I suggested did.

Yep, because this tests cover new approach (with stream, it's also in documentation). To cover deprecated approach I've added RenderTest to test default method of the interface, instead of doing testing for each render implementation.