mailet/base/src/test/java/org/apache/mailet/base/StringUtilsTest.java

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package org.apache.mailet.base;

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

import org.junit.jupiter.api.Test;

import com.google.common.collect.ImmutableList;

class StringUtilsTest {

    @Test
    void listToStringShouldThrowWhenListIsNull() {
        assertThatThrownBy(() -> StringUtils.listToString(null))
            .isInstanceOf(NullPointerException.class);
    }

    @Test
    void listToStringShouldReturnOnlyBracketsWhenListIsEmpty() {
        String listToString = StringUtils.listToString(ImmutableList.<String>of());

        assertThat(listToString).isEqualTo("[]");
    }

    @Test
    void listToStringShouldReturnOneElementWhenListContainsOneElement() {
        String listToString = StringUtils.listToString(ImmutableList.of("first"));

        assertThat(listToString).isEqualTo("[first]");
    }

    @Test
    void listToStringShouldReturnSeparatedElementsWhenListContainsMultipleElements() {
        String listToString = StringUtils.listToString(ImmutableList.of("first", "second", "fourth"));

        assertThat(listToString).isEqualTo("[first, second, fourth]");
    }

    @Test
    void listToStringShouldThrowWhenListContainsANullElement() {
        assertThatThrownBy(() -> StringUtils.listToString(ImmutableList.of("first", null, "fourth")))
            .isInstanceOf(NullPointerException.class);
    }
}