src/test/java/org/apache/commons/lang3/RandomStringUtilsTest.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.greaterThanOrEqualTo;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.lessThanOrEqualTo;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.junit.jupiter.api.Assertions.fail;

import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Random;

import org.junit.jupiter.api.Test;

/**
 * Unit tests {@link org.apache.commons.lang3.RandomStringUtils}.
 */
public class RandomStringUtilsTest {

    //-----------------------------------------------------------------------
    @Test
    public void testConstructor() {
        assertNotNull(new RandomStringUtils());
        final Constructor<?>[] cons = RandomStringUtils.class.getDeclaredConstructors();
        assertEquals(1, cons.length);
        assertTrue(Modifier.isPublic(cons[0].getModifiers()));
        assertTrue(Modifier.isPublic(RandomStringUtils.class.getModifiers()));
        assertFalse(Modifier.isFinal(RandomStringUtils.class.getModifiers()));
    }

    //-----------------------------------------------------------------------
    /**
     * Test the implementation
     */
    @Test
    public void testRandomStringUtils() {
        String r1 = RandomStringUtils.random(50);
        assertEquals(50, r1.length(), "random(50) length");
        String r2 = RandomStringUtils.random(50);
        assertEquals(50, r2.length(), "random(50) length");
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.randomAscii(50);
        assertEquals(50, r1.length(), "randomAscii(50) length");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(r1.charAt(i) >= 32 && r1.charAt(i) <= 127, "char between 32 and 127");
        }
        r2 = RandomStringUtils.randomAscii(50);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.randomAlphabetic(50);
        assertEquals(50, r1.length(), "randomAlphabetic(50)");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(Character.isLetter(r1.charAt(i)) && !Character.isDigit(r1.charAt(i)), "r1 contains alphabetic");
        }
        r2 = RandomStringUtils.randomAlphabetic(50);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.randomAlphanumeric(50);
        assertEquals(50, r1.length(), "randomAlphanumeric(50)");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(Character.isLetterOrDigit(r1.charAt(i)), "r1 contains alphanumeric");
        }
        r2 = RandomStringUtils.randomAlphabetic(50);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.randomGraph(50);
        assertEquals(50, r1.length(), "randomGraph(50) length");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(r1.charAt(i) >= 33 && r1.charAt(i) <= 126, "char between 33 and 126");
        }
        r2 = RandomStringUtils.randomGraph(50);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.randomNumeric(50);
        assertEquals(50, r1.length(), "randomNumeric(50)");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(Character.isDigit(r1.charAt(i)) && !Character.isLetter(r1.charAt(i)), "r1 contains numeric");
        }
        r2 = RandomStringUtils.randomNumeric(50);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.randomPrint(50);
        assertEquals(50, r1.length(), "randomPrint(50) length");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(r1.charAt(i) >= 32 && r1.charAt(i) <= 126, "char between 32 and 126");
        }
        r2 = RandomStringUtils.randomPrint(50);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        String set = "abcdefg";
        r1 = RandomStringUtils.random(50, set);
        assertEquals(50, r1.length(), "random(50, \"abcdefg\")");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(set.indexOf(r1.charAt(i)) > -1, "random char in set");
        }
        r2 = RandomStringUtils.random(50, set);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.random(50, (String) null);
        assertEquals(50, r1.length(), "random(50) length");
        r2 = RandomStringUtils.random(50, (String) null);
        assertEquals(50, r2.length(), "random(50) length");
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        set = "stuvwxyz";
        r1 = RandomStringUtils.random(50, set.toCharArray());
        assertEquals(50, r1.length(), "random(50, \"stuvwxyz\")");
        for (int i = 0; i < r1.length(); i++) {
            assertTrue(set.indexOf(r1.charAt(i)) > -1, "random char in set");
        }
        r2 = RandomStringUtils.random(50, set);
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        r1 = RandomStringUtils.random(50, (char[]) null);
        assertEquals(50, r1.length(), "random(50) length");
        r2 = RandomStringUtils.random(50, (char[]) null);
        assertEquals(50, r2.length(), "random(50) length");
        assertTrue(!r1.equals(r2), "!r1.equals(r2)");

        final long seedMillis = System.currentTimeMillis();
        r1 = RandomStringUtils.random(50, 0, 0, true, true, null, new Random(seedMillis));
        r2 = RandomStringUtils.random(50, 0, 0, true, true, null, new Random(seedMillis));
        assertEquals(r1, r2, "r1.equals(r2)");

        r1 = RandomStringUtils.random(0);
        assertEquals("", r1, "random(0).equals(\"\")");
    }

    @Test
    public void testLANG805() {
        final long seedMillis = System.currentTimeMillis();
        assertEquals("aaa", RandomStringUtils.random(3, 0, 0, false, false, new char[]{'a'}, new Random(seedMillis)));
    }

    @Test
    public void testLANG807() {
        final IllegalArgumentException ex =
                assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(3, 5, 5, false, false));
        final String msg = ex.getMessage();
        assertTrue(msg.contains("start"), "Message (" + msg + ") must contain 'start'");
        assertTrue(msg.contains("end"), "Message (" + msg + ") must contain 'end'");
    }

    @Test
    public void testExceptions() {
        final char[] DUMMY = {'a'}; // valid char array
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1, true, true));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1, DUMMY));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(1, new char[0]));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1, ""));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1, (String) null));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1, 'a', 'z', false, false));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(-1, 'a', 'z', false, false, DUMMY));
        assertThrows(
                IllegalArgumentException.class,
                () -> RandomStringUtils.random(-1, 'a', 'z', false, false, DUMMY, new Random()));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(8, 32, 48, false, true));
        assertThrows(IllegalArgumentException.class, () -> RandomStringUtils.random(8, 32, 65, true, false));
    }

    /**
     * Make sure boundary alphanumeric characters are generated by randomAlphaNumeric
     * This test will fail randomly with probability = 6 * (61/62)**1000 ~ 5.2E-7
     */
    @Test
    public void testRandomAlphaNumeric() {
        final char[] testChars = {'a', 'z', 'A', 'Z', '0', '9'};
        final boolean[] found = {false, false, false, false, false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomAlphanumeric(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            assertTrue(found[i],
                    "alphanumeric character not generated in 1000 attempts: " +
                            testChars[i] + " -- repeated failures indicate a problem ");
        }
    }

    /**
     * Make sure '0' and '9' are generated by randomNumeric
     * This test will fail randomly with probability = 2 * (9/10)**1000 ~ 3.5E-46
     */
    @Test
    public void testRandomNumeric() {
        final char[] testChars = {'0', '9'};
        final boolean[] found = {false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomNumeric(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            assertTrue(found[i],
                    "digit not generated in 1000 attempts: " + testChars[i] +
                            " -- repeated failures indicate a problem ");
        }
    }

    /**
     * Make sure boundary alpha characters are generated by randomAlphabetic
     * This test will fail randomly with probability = 4 * (51/52)**1000 ~ 1.58E-8
     */
    @Test
    public void testRandomAlphabetic() {
        final char[] testChars = {'a', 'z', 'A', 'Z'};
        final boolean[] found = {false, false, false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomAlphabetic(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            assertTrue(found[i],
                    "alphanumeric character not generated in 1000 attempts: " + testChars[i] +
                            " -- repeated failures indicate a problem ");
        }
    }

    /**
     * Make sure 32 and 127 are generated by randomNumeric
     * This test will fail randomly with probability = 2*(95/96)**1000 ~ 5.7E-5
     */
    @Test
    public void testRandomAscii() {
        final char[] testChars = {(char) 32, (char) 126};
        final boolean[] found = {false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomAscii(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            assertTrue(found[i],
                    "ascii character not generated in 1000 attempts: " + (int) testChars[i] +
                            " -- repeated failures indicate a problem");
        }
    }

    @Test
    public void testRandomAsciiRange() {
        final int expectedMinLengthInclusive = 1;
        final int expectedMaxLengthExclusive = 11;
        final String pattern = "^\\p{ASCII}{" + expectedMinLengthInclusive + ',' + expectedMaxLengthExclusive + "}$";

        int maxCreatedLength = expectedMinLengthInclusive;
        int minCreatedLength = expectedMaxLengthExclusive - 1;
        for (int i = 0; i < 1000; i++) {
            final String s = RandomStringUtils.randomAscii(expectedMinLengthInclusive, expectedMaxLengthExclusive);
            assertThat("within range", s.length(), allOf(greaterThanOrEqualTo(expectedMinLengthInclusive), lessThanOrEqualTo(expectedMaxLengthExclusive - 1)));
            assertTrue(s.matches(pattern), s);

            if (s.length() < minCreatedLength) {
                minCreatedLength = s.length();
            }

            if (s.length() > maxCreatedLength) {
                maxCreatedLength = s.length();
            }
        }
        assertThat("min generated, may fail randomly rarely", minCreatedLength, is(expectedMinLengthInclusive));
        assertThat("max generated, may fail randomly rarely", maxCreatedLength, is(expectedMaxLengthExclusive - 1));
    }

    @Test
    public void testRandomAlphabeticRange() {
        final int expectedMinLengthInclusive = 1;
        final int expectedMaxLengthExclusive = 11;
        final String pattern = "^\\p{Alpha}{" + expectedMinLengthInclusive + ',' + expectedMaxLengthExclusive + "}$";

        int maxCreatedLength = expectedMinLengthInclusive;
        int minCreatedLength = expectedMaxLengthExclusive - 1;
        for (int i = 0; i < 1000; i++) {
            final String s = RandomStringUtils.randomAlphabetic(expectedMinLengthInclusive, expectedMaxLengthExclusive);
            assertThat("within range", s.length(), allOf(greaterThanOrEqualTo(expectedMinLengthInclusive), lessThanOrEqualTo(expectedMaxLengthExclusive - 1)));
            assertTrue(s.matches(pattern), s);

            if (s.length() < minCreatedLength) {
                minCreatedLength = s.length();
            }

            if (s.length() > maxCreatedLength) {
                maxCreatedLength = s.length();
            }
        }
        assertThat("min generated, may fail randomly rarely", minCreatedLength, is(expectedMinLengthInclusive));
        assertThat("max generated, may fail randomly rarely", maxCreatedLength, is(expectedMaxLengthExclusive - 1));
    }

    @Test
    public void testRandomAlphanumericRange() {
        final int expectedMinLengthInclusive = 1;
        final int expectedMaxLengthExclusive = 11;
        final String pattern = "^\\p{Alnum}{" + expectedMinLengthInclusive + ',' + expectedMaxLengthExclusive + "}$";

        int maxCreatedLength = expectedMinLengthInclusive;
        int minCreatedLength = expectedMaxLengthExclusive - 1;
        for (int i = 0; i < 1000; i++) {
            final String s = RandomStringUtils.randomAlphanumeric(expectedMinLengthInclusive, expectedMaxLengthExclusive);
            assertThat("within range", s.length(), allOf(greaterThanOrEqualTo(expectedMinLengthInclusive), lessThanOrEqualTo(expectedMaxLengthExclusive - 1)));
            assertTrue(s.matches(pattern), s);

            if (s.length() < minCreatedLength) {
                minCreatedLength = s.length();
            }

            if (s.length() > maxCreatedLength) {
                maxCreatedLength = s.length();
            }
        }
        assertThat("min generated, may fail randomly rarely", minCreatedLength, is(expectedMinLengthInclusive));
        assertThat("max generated, may fail randomly rarely", maxCreatedLength, is(expectedMaxLengthExclusive - 1));
    }

    @Test
    public void testRandomGraphRange() {
        final int expectedMinLengthInclusive = 1;
        final int expectedMaxLengthExclusive = 11;
        final String pattern = "^\\p{Graph}{" + expectedMinLengthInclusive + ',' + expectedMaxLengthExclusive + "}$";

        int maxCreatedLength = expectedMinLengthInclusive;
        int minCreatedLength = expectedMaxLengthExclusive - 1;
        for (int i = 0; i < 1000; i++) {
            final String s = RandomStringUtils.randomGraph(expectedMinLengthInclusive, expectedMaxLengthExclusive);
            assertThat("within range", s.length(), allOf(greaterThanOrEqualTo(expectedMinLengthInclusive), lessThanOrEqualTo(expectedMaxLengthExclusive - 1)));
            assertTrue(s.matches(pattern), s);

            if (s.length() < minCreatedLength) {
                minCreatedLength = s.length();
            }

            if (s.length() > maxCreatedLength) {
                maxCreatedLength = s.length();
            }
        }
        assertThat("min generated, may fail randomly rarely", minCreatedLength, is(expectedMinLengthInclusive));
        assertThat("max generated, may fail randomly rarely", maxCreatedLength, is(expectedMaxLengthExclusive - 1));
    }

    @Test
    public void testRandomNumericRange() {
        final int expectedMinLengthInclusive = 1;
        final int expectedMaxLengthExclusive = 11;
        final String pattern = "^\\p{Digit}{" + expectedMinLengthInclusive + ',' + expectedMaxLengthExclusive + "}$";

        int maxCreatedLength = expectedMinLengthInclusive;
        int minCreatedLength = expectedMaxLengthExclusive - 1;
        for (int i = 0; i < 1000; i++) {
            final String s = RandomStringUtils.randomNumeric(expectedMinLengthInclusive, expectedMaxLengthExclusive);
            assertThat("within range", s.length(), allOf(greaterThanOrEqualTo(expectedMinLengthInclusive), lessThanOrEqualTo(expectedMaxLengthExclusive - 1)));
            assertTrue(s.matches(pattern), s);

            if (s.length() < minCreatedLength) {
                minCreatedLength = s.length();
            }

            if (s.length() > maxCreatedLength) {
                maxCreatedLength = s.length();
            }
        }
        assertThat("min generated, may fail randomly rarely", minCreatedLength, is(expectedMinLengthInclusive));
        assertThat("max generated, may fail randomly rarely", maxCreatedLength, is(expectedMaxLengthExclusive - 1));
    }

    @Test
    public void testRandomPrintRange() {
        final int expectedMinLengthInclusive = 1;
        final int expectedMaxLengthExclusive = 11;
        final String pattern = "^\\p{Print}{" + expectedMinLengthInclusive + ',' + expectedMaxLengthExclusive + "}$";

        int maxCreatedLength = expectedMinLengthInclusive;
        int minCreatedLength = expectedMaxLengthExclusive - 1;
        for (int i = 0; i < 1000; i++) {
            final String s = RandomStringUtils.randomPrint(expectedMinLengthInclusive, expectedMaxLengthExclusive);
            assertThat("within range", s.length(), allOf(greaterThanOrEqualTo(expectedMinLengthInclusive), lessThanOrEqualTo(expectedMaxLengthExclusive - 1)));
            assertTrue(s.matches(pattern), s);

            if (s.length() < minCreatedLength) {
                minCreatedLength = s.length();
            }

            if (s.length() > maxCreatedLength) {
                maxCreatedLength = s.length();
            }
        }
        assertThat("min generated, may fail randomly rarely", minCreatedLength, is(expectedMinLengthInclusive));
        assertThat("max generated, may fail randomly rarely", maxCreatedLength, is(expectedMaxLengthExclusive - 1));
    }

    /**
     * Test homogeneity of random strings generated --
     * i.e., test that characters show up with expected frequencies
     * in generated strings.  Will fail randomly about 1 in 1000 times.
     * Repeated failures indicate a problem.
     */
    @Test
    public void testRandomStringUtilsHomog() {
        final String set = "abc";
        final char[] chars = set.toCharArray();
        String gen = "";
        final int[] counts = {0, 0, 0};
        final int[] expected = {200, 200, 200};
        for (int i = 0; i< 100; i++) {
            gen = RandomStringUtils.random(6, chars);
            for (int j = 0; j < 6; j++) {
                switch (gen.charAt(j)) {
                    case 'a': {
                        counts[0]++;
                        break;
                    }
                    case 'b': {
                        counts[1]++;
                        break;
                    }
                    case 'c': {
                        counts[2]++;
                        break;
                    }
                    default: {
                        fail("generated character not in set");
                    }
                }
            }
        }
        // Perform chi-square test with df = 3-1 = 2, testing at .001 level
        assertTrue(chiSquare(expected, counts) < 13.82, "test homogeneity -- will fail about 1 in 1000 times");
    }

    /**
     * Computes Chi-Square statistic given observed and expected counts
     * @param observed array of observed frequency counts
     * @param expected array of expected frequency counts
     */
    private double chiSquare(final int[] expected, final int[] observed) {
        double sumSq = 0.0d;
        double dev = 0.0d;
        for (int i = 0; i < observed.length; i++) {
            dev = observed[i] - expected[i];
            sumSq += dev * dev / expected[i];
        }
        return sumSq;
    }

    /**
     * Checks if the string got by {@link RandomStringUtils#random(int)}
     * can be converted to UTF-8 and back without loss.
     *
     * @see <a href="https://issues.apache.org/jira/browse/LANG-100">LANG-100</a>
     */
    @Test
    public void testLang100() {
        final int size = 5000;
        final Charset charset = StandardCharsets.UTF_8;
        final String orig = RandomStringUtils.random(size);
        final byte[] bytes = orig.getBytes(charset);
        final String copy = new String(bytes, charset);

        // for a verbose compare:
        for (int i=0; i < orig.length() && i < copy.length(); i++) {
            final char o = orig.charAt(i);
            final char c = copy.charAt(i);
            assertEquals(o, c,
                    "differs at " + i + "(" + Integer.toHexString(Character.valueOf(o).hashCode()) + "," +
                            Integer.toHexString(Character.valueOf(c).hashCode()) + ")");
        }
        // compare length also
        assertEquals(orig.length(), copy.length());
        // just to be complete
        assertEquals(orig, copy);
    }


    /**
     * Test for LANG-1286. Creates situation where old code would
     * overflow a char and result in a code point outside the specified
     * range.
     */
    @Test
    public void testCharOverflow() {
        final int start = Character.MAX_VALUE;
        final int end = Integer.MAX_VALUE;

        @SuppressWarnings("serial")
        final
        Random fixedRandom = new Random() {
            @Override
            public int nextInt(final int n) {
                // Prevents selection of 'start' as the character
                return super.nextInt(n - 1) + 1;
            }
        };

        final String result = RandomStringUtils.random(2, start, end, false, false, null, fixedRandom);
        final int c = result.codePointAt(0);
        assertTrue(c >= start && c < end, String.format("Character '%d' not in range [%d,%d).", c, start, end));
    }
}