Junit and Mockito example

test.java

@Test public void fromCen2FattPAConversionShouldCreateCsvIfConversionResultHasErrors() throws IOException, SyntaxErrorInInvoiceFormatException {

        // given
        given( fromCen.extension() ).willReturn(".xml");

        List<Exception> myErrors = Arrays.asList(new IllegalArgumentException("test exception"));
        //Cen2FattPAConverter fromCen = Mockito.mock(Cen2FattPAConverter.class);
        when(fromCen.convert(any())).thenReturn(new ConversionResult("bytes".getBytes(), myErrors));

        // when converting a mock invoice, errors should occur
        Path outputFolder = FileSystems.getDefault().getPath(outputFolderFile.getAbsolutePath());
        InputStream invoiceSourceFormat = null;
        ConversionCommand sut = new ConversionCommand(ruleRepository, toCen, fromCen, inputInvoice, outputFolder, invoiceSourceFormat);
        PrintStream err = new PrintStream( new ByteArrayOutputStream() );
        PrintStream out = new PrintStream( new ByteArrayOutputStream() );

        // when
        sut.execute(System.out, System.err);

        // then a fromcen-errors.csv should be created for the errors along with the other files
        List<File> files = asList( outputFolderFile.listFiles() );

        assertThat( files + " found", findFirstFileOrNull(outputFolderFile, f -> f.getName().equals("invoice-source.txt")), notNullValue() );
        assertThat( files + " found", findFirstFileOrNull(outputFolderFile, f -> f.getName().equals("invoice-cen.csv")), notNullValue() );
        assertThat( files + " found", findFirstFileOrNull(outputFolderFile, f -> f.getName().equals("invoice-target.xml")), notNullValue() );
        assertThat( files + " found", findFirstFileOrNull(outputFolderFile, f -> f.getName().equals("rule-report.csv")), notNullValue() );
        assertThat( files + " found", findFirstFileOrNull(outputFolderFile, f -> f.getName().equals("invoice-transformation.log")), notNullValue() );

        assertThat( files + " found", findFirstFileOrNull(outputFolderFile, f -> f.getName().equals("fromcen-errors.csv")), notNullValue() );

    }