JavaExercism/exercises/etl/src/test/java/EtlTest.java

import com.google.common.collect.ImmutableMap;
import org.junit.Test;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

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

public class EtlTest {
    private final Etl etl = new Etl();

    @Test
    public void testTransformOneValue() {
        Map<Integer, List<String>> old = ImmutableMap.of(1, Arrays.asList("A"));
        Map<String, Integer> expected = ImmutableMap.of("a", 1);

        assertThat(etl.transform(old)).isEqualTo(expected);
    }

    @Test
    public void testTransformMoreValues() {
        Map<Integer, List<String>> old = ImmutableMap.of(
                1, Arrays.asList("A", "E", "I", "O", "U")
        );
        Map<String, Integer> expected = ImmutableMap.of(
                "a", 1,
                "e", 1,
                "i", 1,
                "o", 1,
                "u", 1
        );

        assertThat(etl.transform(old)).isEqualTo(expected);
    }

    @Test
    public void testMoreKeys() {
        Map<Integer, List<String>> old = ImmutableMap.of(
                1, Arrays.asList("A", "E"),
                2, Arrays.asList("D", "G")
        );
        Map<String, Integer> expected = ImmutableMap.of(
                "a", 1,
                "e", 1,
                "d", 2,
                "g", 2
        );

        assertThat(etl.transform(old)).isEqualTo(expected);
    }

    @Test
    public void testFullDataset() {
        Map<Integer, List<String>> old = ImmutableMap.<Integer, List<String>>builder().
                put(1, Arrays.asList("A", "E", "I", "O", "U", "L", "N", "R", "S", "T")).
                put(2, Arrays.asList("D", "G")).
                put(3, Arrays.asList("B", "C", "M", "P")).
                put(4, Arrays.asList("F", "H", "V", "W", "Y")).
                put(5, Arrays.asList("K")).
                put(8, Arrays.asList("J", "X")).
                put(10, Arrays.asList("Q", "Z")).
                build();
        Map<String, Integer> expected = ImmutableMap.<String, Integer>builder().
                put("a", 1).put("b", 3).put("c", 3).put("d", 2).put("e", 1).
                put("f", 4).put("g", 2).put("h", 4).put("i", 1).put("j", 8).
                put("k", 5).put("l", 1).put("m", 3).put("n", 1).put("o", 1).
                put("p", 3).put("q", 10).put("r", 1).put("s", 1).put("t", 1).
                put("u", 1).put("v", 4).put("w", 4).put("x", 8).put("y", 4).
                put("z", 10).build();

        assertThat(etl.transform(old)).isEqualTo(expected);
    }
}