Update tests

Author: captainsafia

src/OpenApi/test/OpenApiGeneratorTests.cs

@@ -170,7 +170,7 @@ public void AddsMultipleResponseFormatsFromMetadataWithPoco()
         var content = Assert.Single(createdResponseType.Content);
 
         Assert.NotNull(createdResponseType);
-        Assert.Equal("object", content.Value.Schema.Type);
+        Assert.Equal("string", content.Value.Schema.Type);
         Assert.Equal("application/json", createdResponseType.Content.Keys.First());
 
         var badRequestResponseType = responses["400"];

src/OpenApi/test/OpenApiSchemaGeneratorTests.cs

@@ -0,0 +1,111 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+using System.Text.Json.Nodes;
+using Microsoft.AspNetCore.OpenApi;
+
+namespace Microsoft.AspNetCore.OpenApi.Tests;
+
+public class  OpenApiSchemaGeneratorTests
+{
+    [Theory]
+    [InlineData(typeof(Dictionary<string, string>))]
+    [InlineData(typeof(Todo))]
+    public void CanGenerateCorrectSchemaForDictionaryTypes(Type type)
+    {
+        var schema = OpenApiSchemaGenerator.GetOpenApiSchema(type);
+        Assert.NotNull(schema);
+        Assert.Equal("object", schema.Type);
+    }
+
+    [Theory]
+    [InlineData(typeof(IList<string>))]
+    [InlineData(typeof(Products))]
+    public void CanGenerateSchemaForListTypes(Type type)
+    {
+        var schema = OpenApiSchemaGenerator.GetOpenApiSchema(type);
+        Assert.NotNull(schema);
+        Assert.Equal("array", schema.Type);
+    }
+
+    [Theory]
+    [InlineData(typeof(DateTime))]
+    [InlineData(typeof(DateTimeOffset))]
+    public void CanGenerateSchemaForDateTimeTypes(Type type)
+    {
+        var schema = OpenApiSchemaGenerator.GetOpenApiSchema(type);
+        Assert.NotNull(schema);
+        Assert.Equal("string", schema.Type);
+        Assert.Equal("date-time", schema.Format);
+    }
+
+    [Fact]
+    public void CanGenerateSchemaForDateSpanTypes()
+    {
+        var schema = OpenApiSchemaGenerator.GetOpenApiSchema(typeof(TimeSpan));
+        Assert.NotNull(schema);
+        Assert.Equal("string", schema.Type);
+        Assert.Equal("date-span", schema.Format);
+    }
+
+    class Todo : Dictionary<string, object> { }
+    class Products : IList<int>
+    {
+        public int this[int index] { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
+
+        public int Count => throw new NotImplementedException();
+
+        public bool IsReadOnly => throw new NotImplementedException();
+
+        public void Add(int item)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Clear()
+        {
+            throw new NotImplementedException();
+        }
+
+        public bool Contains(int item)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void CopyTo(int[] array, int arrayIndex)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IEnumerator<int> GetEnumerator()
+        {
+            throw new NotImplementedException();
+        }
+
+        public int IndexOf(int item)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Insert(int index, int item)
+        {
+            throw new NotImplementedException();
+        }
+
+        public bool Remove(int item)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void RemoveAt(int index)
+        {
+            throw new NotImplementedException();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}