Add explicit test for hash collision handling. (#11)

Author: jlao

UnitTests/BadHashCode.cs

@@ -0,0 +1,13 @@
+namespace UnitTests
+{
+    struct BadHashCode
+    {
+        public int Value;
+
+        public override int GetHashCode() => 42;
+
+        public static implicit operator BadHashCode(int i) => new BadHashCode { Value = i };
+
+        public static implicit operator int(BadHashCode bhc) => bhc.Value;
+    }
+}

UnitTests/CacheTableTestBase.cs

@@ -8,7 +8,7 @@
 
 namespace UnitTests
 {
-    public abstract class CacheTableTestBase<TCacheTable> where TCacheTable : ICacheTable<int, int>
+    public abstract class CacheTableTestBase
     {
         protected ITestOutputHelper output;
 
@@ -17,12 +17,12 @@ protected CacheTableTestBase(ITestOutputHelper output)
             this.output = output;
         }
 
-        protected abstract TCacheTable CreateTable(int numRows, int numColumns);
+        protected abstract ICacheTable<TKey, TValue> CreateTable<TKey, TValue>(int numRows, int numColumns);
 
         [Fact]
         public void SetAndTryGetValue()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             table[1] = 2;
             table.TryGetValue(1, out int val).Should().BeTrue();
             val.Should().Be(2);
@@ -31,23 +31,23 @@ public void SetAndTryGetValue()
         [Fact]
         public void TryGetNonExistentValue()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             table.TryGetValue(1, out int val).Should().BeFalse();
             val.Should().Be(default(int));
         }
 
         [Fact]
         public void SetAndIndex()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             table[1] = 2;
             table[1].Should().Be(2);
         }
 
         [Fact]
         public void Update()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
 
             for (int i = 0; i < 4; i++)
             {
@@ -72,7 +72,7 @@ public void Update()
         [Fact]
         public void IndexNonExistentKeyThrows()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             Action act = () => Console.WriteLine(table[0]);
             act.Should().Throw<KeyNotFoundException>()
                 .WithMessage("No value found for 0");
@@ -81,7 +81,7 @@ public void IndexNonExistentKeyThrows()
         [Fact]
         public void ContainsKey()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             table.ContainsKey(0).Should().BeFalse();
             table[0] = 1;
             table.ContainsKey(0).Should().BeTrue();
@@ -90,7 +90,7 @@ public void ContainsKey()
         [Fact]
         public void Remove()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             table[1] = 2;
             table.Remove(1).Should().BeTrue();
             table.TryGetValue(1, out int val).Should().BeFalse();
@@ -103,7 +103,7 @@ public void Clear()
         {
             const int numInserts = 40;
 
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             for (int i = 0; i < numInserts; i++)
             {
                 table[i] = i;
@@ -123,7 +123,7 @@ public void Clear()
         [Fact]
         public void Count()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             table.Count.Should().Be(0);
 
             for (int i = 0; i < 4; i++)
@@ -142,7 +142,7 @@ public void Count()
         [Fact]
         public void Enumerate()
         {
-            var table = this.CreateTable(10, 4);
+            var table = this.CreateTable<int, int>(10, 4);
             var rng = new Random();
             List<KeyValuePair<int, int>> expected = new List<KeyValuePair<int, int>>();
 
@@ -160,7 +160,7 @@ public void Enumerate()
         [Fact]
         public void InsertOnFullTableOverwrites()
         {
-            var table = this.CreateTable(5, 4);
+            var table = this.CreateTable<int, int>(5, 4);
 
             int i = 0;
             do
@@ -183,5 +183,28 @@ public void InsertOnFullTableOverwrites()
             after.Count.Should().Be(1);
             after.First().Should().Be(i);
         }
+
+        [Theory]
+        [InlineData(4)]
+        [InlineData(7)]
+        public void ResolvesHashCollisions(int numColumns)
+        {
+            var table = this.CreateTable<BadHashCode, int>(5, numColumns);
+
+            for (int i = 0; i < numColumns; i++)
+            {
+                table[i] = i;
+            }
+
+            for (int i = 0; i < numColumns; i++)
+            {
+                table[i].Should().Be(i);
+            }
+
+            // This is going to overwrite a value
+            table[numColumns] = numColumns;
+            table[numColumns].Should().Be(numColumns);
+            table.Count.Should().Be(numColumns);
+        }
     }
 }

UnitTests/CacheTableTests.cs

@@ -3,15 +3,15 @@
 
 namespace UnitTests
 {
-    public class CacheTableTests : CacheTableTestBase<CacheTable<int, int>>
+    public class CacheTableTests : CacheTableTestBase
     {
         public CacheTableTests(ITestOutputHelper output) : base(output)
         {
         }
 
-        protected override CacheTable<int, int> CreateTable(int numRows, int numColumns)
+        protected override ICacheTable<TKey, TValue> CreateTable<TKey, TValue>(int numRows, int numColumns)
         {
-            return new CacheTable<int, int>(numRows, numColumns);
+            return new CacheTable<TKey, TValue>(numRows, numColumns);
         }
     }
 }

UnitTests/ConcurrentCacheTableTests.cs

@@ -6,21 +6,21 @@
 
 namespace UnitTests
 {
-    public class ConcurrentCacheTableTests : CacheTableTestBase<ConcurrentCacheTable<int, int>>
+    public class ConcurrentCacheTableTests : CacheTableTestBase
     {
         public ConcurrentCacheTableTests(ITestOutputHelper output) : base(output)
         {
         }
 
-        protected override ConcurrentCacheTable<int, int> CreateTable(int numRows, int numColumns)
+        protected override ICacheTable<TKey, TValue> CreateTable<TKey, TValue>(int numRows, int numColumns)
         {
-            return new ConcurrentCacheTable<int, int>(numRows, numColumns, 3);
+            return new ConcurrentCacheTable<TKey, TValue>(numRows, numColumns, 3);
         }
 
         [Fact]
         public async Task ConcurrentWrites()
         {
-            var table = CreateTable(5, 4);
+            var table = this.CreateTable<int, int>(5, 4);
 
             const int numWrites = 1000;