diff --git a/Refit.Tests/RestServiceExceptions.cs b/Refit.Tests/RestServiceExceptions.cs
new file mode 100644
index 000000000..fabf5f0b1
--- /dev/null
+++ b/Refit.Tests/RestServiceExceptions.cs
@@ -0,0 +1,174 @@
+using Xunit;
+// ReSharper disable InconsistentNaming
+
+namespace Refit.Tests;
+
+public interface IManyCancellationTokens
+{
+    [Get("/")]
+    Task<string> GetValue(CancellationToken token0, CancellationToken token1);
+}
+
+public interface IManyHeaderCollections
+{
+    [Get("/")]
+    Task<string> GetValue([HeaderCollection] IDictionary<string, string> collection0, [HeaderCollection] IDictionary<string, string> collection1);
+}
+
+public interface IHeaderCollectionWrongType
+{
+    [Get("/")]
+    Task<string> GetValue([HeaderCollection] IDictionary<string, object> collection);
+}
+
+public interface IDoesNotStartSlash
+{
+    [Get("users")]
+    Task<string> GetValue();
+}
+
+public interface IUrlContainsCRLF
+{
+    [Get("/\r")]
+    Task<string> GetValue();
+}
+
+public interface IRoundTripNotString
+{
+    [Get("/{**value}")]
+    Task<string> GetValue(int value);
+}
+
+public interface IUrlNoMatchingParameters
+{
+    [Get("/{value}")]
+    Task<string> GetValue();
+}
+
+public interface IMultipartAndBody
+{
+    [Get("/}")]
+    [Multipart]
+    Task<string> GetValue([Body] string body);
+}
+
+public interface IManyBody
+{
+    [Get("/")]
+    Task<string> GetValue([Body] string body0, [Body] string body1);
+}
+
+public class UserBody
+{
+    public string Value { get; set; }
+}
+
+public interface IManyComplexTypes
+{
+    [Post("/")]
+    Task<string> PostValue(UserBody body0, UserBody body1);
+}
+
+public interface IManyAuthorize
+{
+    [Get("/")]
+    Task<string> GetValue([Authorize("Bearer")] string token0, [Authorize("Bearer")] string token1);
+}
+
+public interface IInvalidReturnType
+{
+    [Get("/")]
+    string GetValue();
+}
+
+public class RestServiceExceptionTests
+{
+    [Fact]
+    public void ManyCancellationTokensShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IManyCancellationTokens>("https://api.github.com"));
+        AssertExceptionContains("only contain a single CancellationToken", exception);
+    }
+
+    [Fact]
+    public void ManyHeaderCollectionShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IManyHeaderCollections>("https://api.github.com"));
+        AssertExceptionContains("Only one parameter can be a HeaderCollection parameter", exception);
+    }
+
+    [Fact]
+    public void InvalidHeaderCollectionTypeShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IHeaderCollectionWrongType>("https://api.github.com"));
+        AssertExceptionContains("HeaderCollection parameter of type", exception);
+    }
+
+    [Fact]
+    public void UrlDoesntStartWithSlashShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IDoesNotStartSlash>("https://api.github.com"));
+        AssertExceptionContains("must start with '/' and be of the form", exception);
+    }
+
+    [Fact]
+    public void UrlContainsCRLFShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IUrlContainsCRLF>("https://api.github.com"));
+        AssertExceptionContains("must not contain CR or LF characters", exception);
+    }
+
+    [Fact]
+    public void RoundTripParameterNotStringShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IRoundTripNotString>("https://api.github.com"));
+        AssertExceptionContains("has round-tripping parameter", exception);
+    }
+
+    [Fact]
+    public void UrlNoMatchingParameterShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IUrlNoMatchingParameters>("https://api.github.com"));
+        AssertExceptionContains("but no method parameter matches", exception);
+    }
+
+    [Fact]
+    public void MultipartAndBodyShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IMultipartAndBody>("https://api.github.com"));
+        AssertExceptionContains("Multipart requests may not contain a Body parameter", exception);
+    }
+
+    [Fact]
+    public void ManyBodyShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IManyBody>("https://api.github.com"));
+        AssertExceptionContains("Only one parameter can be a Body parameter", exception);
+    }
+
+    [Fact]
+    public void ManyComplexTypesShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IManyComplexTypes>("https://api.github.com"));
+        AssertExceptionContains("Multiple complex types found. Specify one parameter as the body using BodyAttribute", exception);
+    }
+
+    [Fact]
+    public void ManyAuthorizeAttributesShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IManyAuthorize>("https://api.github.com"));
+        AssertExceptionContains("Only one parameter can be an Authorize parameter", exception);
+    }
+
+    [Fact]
+    public void InvalidReturnTypeShouldThrow()
+    {
+        var exception = Assert.Throws<ArgumentException>(() => RestService.For<IInvalidReturnType>("https://api.github.com"));
+        AssertExceptionContains("is invalid. All REST Methods must return either Task<T> or ValueTask<T> or IObservable<T>", exception);
+    }
+
+    private static void AssertExceptionContains(string expectedSubstring, Exception exception)
+    {
+        Assert.Contains(expectedSubstring, exception.Message!, StringComparison.Ordinal);
+    }
+}