src/Lucene.Net.TestFramework/Support/Util/LuceneRandomSeedInitializer.cs

using NUnit.Framework.Interfaces;
using NUnit.Framework.Internal;
using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Reflection;

namespace Lucene.Net.Util
{
    /*
     * 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.
     */

    internal class LuceneRandomSeedInitializer
    {
        #region Messages

        const string RANDOM_SEED_PARAMS_MSG =
            "\"tests:seed\" parameter must be a valid long hexadecimal value or the word \"random\".";

        #endregion

        private J2N.Randomizer random;
        private long initialSeed;
        private long? testSeed;

        /// <summary>
        /// Tries to get the random seed from either a <see cref="RandomSeedAttribute"/> or the "tests:seed" system property.
        /// If niether of these exist, a random seed will be generated and this method returns <c>false</c>;
        /// </summary>
        /// <param name="test">The test fixture.</param>
        /// <param name="seed">The random seed for a new <see cref="Random"/> instance.
        /// Note this is a subclass of <see cref="Random"/>, since the default doesn't produce consistent results across platforms.</param>
        /// <returns><c>true</c> if the seed was found in context; <c>false</c> if the seed was generated.</returns>
        private static bool TryGetRandomSeedsFromContext(Test test, out long seed, out long? testSeed)
        {
            //bool generate;
            seed = default;
            testSeed = default;
            string seedAsString;

            var randomSeedAttribute = (RandomSeedAttribute)test.TypeInfo.Assembly
                .GetCustomAttributes(typeof(RandomSeedAttribute), inherit: false)
                .FirstOrDefault();
            if (randomSeedAttribute != null)
            {
                seedAsString = randomSeedAttribute.RandomSeed;
                //generate = false;
            }
            else
            {
                // For now, ignore anything NUnit3TestAdapter does, because it is messing up repeatable runs.
                seedAsString = SystemProperties.GetProperty("tests:seed", null);
            }

            if (seedAsString is null || "random".Equals(seedAsString, StringComparison.OrdinalIgnoreCase))
            {
                //generate = true;
                return false;
            }

            int colonIndex = seedAsString.IndexOf(':');
            if (colonIndex  != -1)
            {
                if (!J2N.Numerics.Int64.TryParse(seedAsString, 0, colonIndex, radix: 16, out seed))
                {
                    test.MakeInvalid(RANDOM_SEED_PARAMS_MSG);
                    return false;
                }

                // LUCENENET TODO: For now, we are ignoring anything after a colon in the string, but logically it seems like
                // a second seed would be to set the a test so the RandomAttribute fails on the first iteration. Lucene uses a compound
                // seed, but it isn't clear from analyzing the source how it is used, just that it can contain any number of colon delimited
                // values. If we ignore now, we leave the door open for adding a compound seed in the most sensible way later without breaking
                // the current version when the change is introduced.
                //if (!J2N.Numerics.Int64.TryParse(seedAsString, colonIndex + 1, seedAsString.Length - (colonIndex + 1), radix: 16, out long testSeedValue))
                //{
                //    test.MakeInvalid(RANDOM_SEED_PARAMS_MSG);
                //    return false;
                //}

                //testSeed = testSeedValue;
                return true;
            }
            else if (J2N.Numerics.Int64.TryParse(seedAsString, radix: 16, out seed))
            {
                return true;
            }

            test.MakeInvalid(RANDOM_SEED_PARAMS_MSG);
            return false;
        }

        /// <summary>
        /// Initializes the randomized context and seed for the test fixture.
        /// </summary>
        /// <param name="fixture">The test fixture.</param>
        /// <param name="seedOffset">Offset that will be added to the initial seed. This should be different for SetUpFixture and TestFixture attributes
        /// so they have different seeds that are deterministically based on the initial seed.</param>
        /// <returns>The randomized context.</returns>
        public RandomizedContext InitializeTestFixture(Test fixture, Assembly testAssembly, int seedOffset = 0)
        {
            if (fixture is null)
                throw new ArgumentNullException(nameof(fixture));

            if (!TryGetRandomSeedsFromContext(fixture, out initialSeed, out testSeed)) // NOTE: This sets the initialSeed and testSeed fields for this class.
                initialSeed = new J2N.Randomizer().NextInt64(); // Seed not configured or explicitly set to "random", so auto-generate

            random = new J2N.Randomizer(initialSeed + seedOffset);

            int goodFastHashSeed = (int)initialSeed * 31; // LUCENENET: Multiplying 31 to remove the possility of a collision with the test framework while still using a deterministic number.
            if (StringHelper.goodFastHashSeed != goodFastHashSeed)
                StringHelper.goodFastHashSeed = goodFastHashSeed;

            // Now we need to generate the first seed for our test fixture
            // which will be used during OneTimeSetUp and OneTimeTearDown.
            // Assumption: The passed in fixture doesn't have any tests added.
            // The tests are added in a later step to prevent differences in the
            // result when there are filters applied.

            // Generate a new long value that is the seed for this specific test.
            return InitializeTestFixture(fixture, new RandomizedContext(fixture, testAssembly, initialSeed, testSeed ?? random.NextInt64()));
        }

        /// <summary>
        /// Initializes the randomized context for the fixture.
        /// </summary>
        /// <param name="fixture">The test fixture.</param>
        /// <param name="randomizedContext">The randomized context to associate with the fixture.</param>
        /// <returns>The randomized context.</returns>
        [SuppressMessage("Performance", "CA1822:Mark members as static", Justification = "By design")]
        public RandomizedContext InitializeTestFixture(Test fixture, RandomizedContext randomizedContext)
        {
            if (fixture is null)
                throw new ArgumentNullException(nameof(fixture));

            fixture.Properties.Set(RandomizedContext.RandomizedContextPropertyName, randomizedContext);
            return randomizedContext;
        }

        /// <summary>
        /// Generates random seeds for the given test and all of its children that
        /// can be cast to <see cref="Test"/>.
        /// </summary>
        /// <param name="test"></param>
        public void GenerateRandomSeeds(Test test)
        {
            SetRandomSeeds(test);
        }

        private void SetRandomSeeds(Test test)
        {
            if (test is null)
                return;

            var testAssembly = test is ParameterizedMethodSuite ? test.Tests[0].TypeInfo.Assembly : test.TypeInfo.Assembly;

            test.Properties.Set(
                RandomizedContext.RandomizedContextPropertyName,
                // Generate a new long value that is the seed for this specific test.
                new RandomizedContext(test, testAssembly, initialSeed, testSeed ?? random.NextInt64()));

            if (test.HasChildren)
            {
                foreach (ITest child in test.Tests)
                    if (child is Test testChild)
                        SetRandomSeeds(testChild);
            }
        }
    }
}