Added tests for DisplayApp

package cz.muni.fi.pb162.hw01.impl.app;

import com.github.stefanbirkner.systemlambda.SystemLambda;

import cz.muni.fi.pb162.hw01.impl.Outputs;

import org.junit.jupiter.api.Test;

import static org.assertj.core.api.Assertions.assertThat;

public class DisplayAppTest {

    private static DisplayApp app = new DisplayApp();

    @Test

    public void shouldPrintEmptyDisplay() throws Exception {

        assertApplicationRun(1, "", Outputs.TXT_);

    }

    @Test

    public void shouldContainMultipleSymbols() throws Exception {

        assertApplicationRun(11, "0123456789E", Outputs.TXT_0123456789E);

    }

    @Test

    public void shouldHandleLongerInput() throws Exception {

        assertApplicationRun(4, "0123456789E", Outputs.TXT_0123);

    }

    @Test

    public void shouldHandleUnknownSymbol() throws Exception {

        assertApplicationRun(4, "01k2", Outputs.TXT_01E2);

    }

    @Test

    public void shouldHandleShorterInput() throws Exception {

        assertApplicationRun(6, "8012", Outputs.TXT_8012_);

    }

    private static String run(DisplayAppOptions options) throws Exception {

        return SystemLambda.tapSystemOut(() -> app.run(options));

    }

    private void assertApplicationRun(int size, String text, String expected) throws Exception {

        var actual = run(new DisplayAppOptions(size, text));

        assertThat(removeSuffixNewLine(actual)).isEqualTo(removeSuffixNewLine(expected));

    }

    private static String removeSuffixNewLine(String string) {

        if (string.endsWith(System.lineSeparator())) {

            return string.substring(0, string.length() - 1);

        }

        return string;

    }

}