Add AssertionContext (#167)

* Add AssertionContext * Update docs
JasperFx · Jul 26, 2024 · fbdc3bc · fbdc3bc
1 parent 1ae5e66
commit fbdc3bc
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diff --git a/docs/scenarios/assertions.md b/docs/scenarios/assertions.md
@@ -6,7 +6,7 @@ failures will be reported out in the Exception message thrown by Alba on Scenari
 :::
 
 The Scenario assertions in Alba are completely extensible and you can happily add your own via extension methods - but
-please send anything that's generally useful as a pull request to Alba itself;-)
+please send anything that's generally useful as a pull request to Alba itself ;-)
 
 The first step is to write your own implementation of this interface:
 
@@ -15,7 +15,7 @@ The first step is to write your own implementation of this interface:
 ```cs
 public interface IScenarioAssertion
 {
-    void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex);
+    void Assert(Scenario scenario, AssertionContext context);
 }
 ```
 <sup><a href='https://github.com/JasperFx/alba/blob/master/src/Alba/IScenarioAssertion.cs#L5-L10' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_iscenarioassertion' title='Start of snippet'>anchor</a></sup>
@@ -35,19 +35,21 @@ internal sealed class BodyContainsAssertion : IScenarioAssertion
         Text = text;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var body = ex.ReadBody(context);
+        // Context has this useful extension to read the body as a string.
+        // This will bake the body contents into the exception message to make debugging easier.
+        var body = context.ReadBodyAsString();
         if (!body.Contains(Text))
         {
             // Add the failure message to the exception. This exception only
             // gets thrown if there are failures.
-            ex.Add($"Expected text '{Text}' was not found in the response body");
+            context.AddFailure($"Expected text '{Text}' was not found in the response body");
         }
     }
 }
 ```
-<sup><a href='https://github.com/JasperFx/alba/blob/master/src/Alba/Assertions/BodyContainsAssertion.cs#L5-L26' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_bodycontainsassertion' title='Start of snippet'>anchor</a></sup>
+<sup><a href='https://github.com/JasperFx/alba/blob/master/src/Alba/Assertions/BodyContainsAssertion.cs#L5-L28' title='Snippet source file'>snippet source</a> | <a href='#snippet-sample_bodycontainsassertion' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 Once you have your assertion class, you can apply it to a scenario through an extension method against the 

diff --git a/src/Alba.Testing/Assertions/AssertionRunner.cs b/src/Alba.Testing/Assertions/AssertionRunner.cs
@@ -21,7 +21,7 @@ public static ScenarioAssertionException Run(IScenarioAssertion assertion,
             var stream = context.Response.Body;
             stream.Position = 0;
 
-            assertion.Assert(null, context, ex);
+            assertion.Assert(null, new AssertionContext(context, ex));
 
             return ex;
         }

diff --git a/src/Alba.Testing/ScenarioAssertionExceptionTests.cs b/src/Alba.Testing/ScenarioAssertionExceptionTests.cs
@@ -1,4 +1,7 @@
-using Shouldly;
+using System;
+using System.IO;
+using Microsoft.AspNetCore.Http;
+using Shouldly;
 using Xunit;
 
 namespace Alba.Testing
@@ -37,16 +40,21 @@ public void all_messages_are_in_the_ex_message()
         public void show_the_body_in_the_message_if_set()
         {
             var ex = new ScenarioAssertionException();
+            var ctx = new DefaultHttpContext();
+            ctx.Response.Body = new MemoryStream();
+            var body = "<html></html>";
+            using var sw = new StreamWriter(ctx.Response.Body);
+            sw.Write(body);
+            sw.Flush();
+
+            var context = new AssertionContext(ctx, ex);
             ex.Add("You stink!");
 
             ex.Message.ShouldNotContain("Actual body text was:");
 
-            ex.Body = "<html></html>";
-
-
-
+            context.ReadBodyAsString();
             ex.Message.ShouldContain("Actual body text was:");
-            ex.Message.ShouldContain(ex.Body);
+            ex.Message.ShouldContain(body);
         }
     }
 }
diff --git a/src/Alba/AssertionContext.cs b/src/Alba/AssertionContext.cs
@@ -0,0 +1,65 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+using Alba.Internal;
+using Microsoft.AspNetCore.Http;
+
+namespace Alba;
+
+public sealed class AssertionContext
+{
+    private readonly ScenarioAssertionException _assertionException;
+    public HttpContext HttpContext { get; }
+    public AssertionContext(HttpContext httpContext, ScenarioAssertionException assertionException)
+    {
+        HttpContext = httpContext;
+        _assertionException = assertionException;
+    }
+
+    /// <summary>
+    /// Add an assertion failure message
+    /// </summary>
+    /// <param name="message"></param>
+    public void AddFailure(string message) => _assertionException.Add(message);
+
+    private string? _body;
+
+    /// <summary>
+    /// Reads the response body and returns it as a string
+    /// </summary>
+    /// <returns>A string with the content of the body</returns>
+    [MemberNotNull(nameof(_body))]
+    public string ReadBodyAsString()
+    {
+        // Hardening for GH-95
+        try
+        {
+            var stream = HttpContext.Response.Body;
+            if (_body == null)
+            {
+                if (stream.CanSeek)
+                {
+                    stream.Position = 0;
+                }
+
+                _body = Encoding.UTF8.GetString(stream.ReadAllBytes());
+
+                // reset the position so users can do follow up activities without tripping up.
+                if (stream.CanSeek)
+                {
+                    stream.Position = 0;
+                }
+
+                _assertionException.AddBody(_body);
+            }
+        }
+        catch (Exception)
+        {
+            _body = string.Empty;
+        }
+
+        return _body;
+    }
+
+
+}
diff --git a/src/Alba/Assertions/BodyContainsAssertion.cs b/src/Alba/Assertions/BodyContainsAssertion.cs
@@ -12,14 +12,16 @@ public BodyContainsAssertion(string text)
         Text = text;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var body = ex.ReadBody(context);
+        // Context has this useful extension to read the body as a string.
+        // This will bake the body contents into the exception message to make debugging easier.
+        var body = context.ReadBodyAsString();
         if (!body.Contains(Text))
         {
             // Add the failure message to the exception. This exception only
             // gets thrown if there are failures.
-            ex.Add($"Expected text '{Text}' was not found in the response body");
+            context.AddFailure($"Expected text '{Text}' was not found in the response body");
         }
     }
 }

diff --git a/src/Alba/Assertions/BodyDoesNotContainAssertion.cs b/src/Alba/Assertions/BodyDoesNotContainAssertion.cs
@@ -11,12 +11,12 @@ public BodyDoesNotContainAssertion(string text)
         Text = text;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var body = ex.ReadBody(context);
+        var body = context.ReadBodyAsString();
         if (body.Contains(Text))
         {
-            ex.Add($"Text '{Text}' should not be found in the response body");
+            context.AddFailure($"Text '{Text}' should not be found in the response body");
         }
     }
 }
diff --git a/src/Alba/Assertions/BodyTextAssertion.cs b/src/Alba/Assertions/BodyTextAssertion.cs
@@ -11,12 +11,12 @@ public BodyTextAssertion(string text)
         Text = text;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var body = ex.ReadBody(context);
+        var body = context.ReadBodyAsString();
         if (!body.Equals(Text))
         {
-            ex.Add($"Expected the content to be '{Text}'");
+            context.AddFailure($"Expected the content to be '{Text}'");
         }
     }
 }
diff --git a/src/Alba/Assertions/HasSingleHeaderValueAssertion.cs b/src/Alba/Assertions/HasSingleHeaderValueAssertion.cs
@@ -12,14 +12,14 @@ public HasSingleHeaderValueAssertion(string headerKey)
         _headerKey = headerKey;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var values = context.Response.Headers[_headerKey];
+        var values = context.HttpContext.Response.Headers[_headerKey];
 
         switch (values.Count)
         {
             case 0:
-                ex.Add(
+                context.AddFailure(
                     $"Expected a single header value of '{_headerKey}', but no values were found on the response");
                 break;
             case 1:
@@ -28,7 +28,7 @@ public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionExce
 
             default:
                 var valueText = values.Select(x => "'" + x + "'").Aggregate((s1, s2) => $"{s1}, {s2}");
-                ex.Add($"Expected a single header value of '{_headerKey}', but found multiple values on the response: {valueText}");
+                context.AddFailure($"Expected a single header value of '{_headerKey}', but found multiple values on the response: {valueText}");
                 break;
         }
     }

diff --git a/src/Alba/Assertions/HeaderExistsAssertion.cs b/src/Alba/Assertions/HeaderExistsAssertion.cs
@@ -11,13 +11,13 @@ public HeaderExistsAssertion(string headerKey)
         _headerKey = headerKey;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var values = context.Response.Headers[_headerKey];
+        var values = context.HttpContext.Response.Headers[_headerKey];
 
         if (values.Count == 0)
         {
-            ex.Add($"Expected header '{_headerKey}' to be present but no values were found on the response.");
+            context.AddFailure($"Expected header '{_headerKey}' to be present but no values were found on the response.");
         }
 
     }

diff --git a/src/Alba/Assertions/HeaderMatchAssertion.cs b/src/Alba/Assertions/HeaderMatchAssertion.cs
@@ -15,27 +15,27 @@ public HeaderMatchAssertion(string headerKey, Regex regex)
         _regex = regex;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var values = context.Response.Headers[_headerKey];
+        var values = context.HttpContext.Response.Headers[_headerKey];
 
         switch (values.Count)
         {
             case 0:
-                ex.Add($"Expected a single header value of '{_headerKey}' matching '{_regex}', but no values were found on the response");
+                context.AddFailure($"Expected a single header value of '{_headerKey}' matching '{_regex}', but no values were found on the response");
                 break;
 
             case 1:
                 var actual = values.Single();
                 if (_regex.IsMatch(actual) == false)
                 {
-                    ex.Add($"Expected a single header value of '{_headerKey}' matching '{_regex}', but the actual value was '{actual}'");
+                    context.AddFailure($"Expected a single header value of '{_headerKey}' matching '{_regex}', but the actual value was '{actual}'");
                 }
                 break;
 
             default:
                 var valueText = values.Select(x => "'" + x + "'").Aggregate((s1, s2) => $"{s1}, {s2}");
-                ex.Add($"Expected a single header value of '{_headerKey}' matching '{_regex}', but the actual values were {valueText}");
+                context.AddFailure($"Expected a single header value of '{_headerKey}' matching '{_regex}', but the actual values were {valueText}");
                 break;
         }
     }

diff --git a/src/Alba/Assertions/HeaderMultiValueAssertion.cs b/src/Alba/Assertions/HeaderMultiValueAssertion.cs
@@ -15,22 +15,22 @@ public HeaderMultiValueAssertion(string headerKey, IEnumerable<string> expected)
         _expected = expected.ToList();
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var values = context.Response.Headers[_headerKey];
+        var values = context.HttpContext.Response.Headers[_headerKey];
         var expectedText = _expected.Select(x => "'" + x + "'").Aggregate((s1, s2) => $"{s1}, {s2}");
 
         switch (values.Count)
         {
             case 0:
-                ex.Add($"Expected header values of '{_headerKey}'={expectedText}, but no values were found on the response.");
+                context.AddFailure($"Expected header values of '{_headerKey}'={expectedText}, but no values were found on the response.");
                 break;
 
             default:
                 if (!_expected.All(x => values.Contains(x)))
                 {
                     var valueText = values.Select(x => "'" + x + "'").Aggregate((s1, s2) => $"{s1}, {s2}");
-                    ex.Add($"Expected header values of '{_headerKey}'={expectedText}, but the actual values were {valueText}.");
+                    context.AddFailure($"Expected header values of '{_headerKey}'={expectedText}, but the actual values were {valueText}.");
                 }
                 break;
         }

diff --git a/src/Alba/Assertions/HeaderValueAssertion.cs b/src/Alba/Assertions/HeaderValueAssertion.cs
@@ -14,27 +14,27 @@ public HeaderValueAssertion(string headerKey, string expected)
         _expected = expected;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var values = context.Response.Headers[_headerKey];
+        var values = context.HttpContext.Response.Headers[_headerKey];
 
         switch (values.Count)
         {
             case 0:
-                ex.Add($"Expected a single header value of '{_headerKey}'='{_expected}', but no values were found on the response");
+                context.AddFailure($"Expected a single header value of '{_headerKey}'='{_expected}', but no values were found on the response");
                 break;
 
             case 1:
                 var actual = values.Single();
                 if (actual != _expected)
                 {
-                    ex.Add($"Expected a single header value of '{_headerKey}'='{_expected}', but the actual value was '{actual}'");
+                    context.AddFailure($"Expected a single header value of '{_headerKey}'='{_expected}', but the actual value was '{actual}'");
                 }
                 break;
 
             default:
                 var valueText = values.Select(x => "'" + x + "'").Aggregate((s1, s2) => $"{s1}, {s2}");
-                ex.Add($"Expected a single header value of '{_headerKey}'='{_expected}', but the actual values were {valueText}");
+                context.AddFailure($"Expected a single header value of '{_headerKey}'='{_expected}', but the actual values were {valueText}");
                 break;
         }
 

diff --git a/src/Alba/Assertions/NoHeaderValueAssertion.cs b/src/Alba/Assertions/NoHeaderValueAssertion.cs
@@ -12,14 +12,14 @@ public NoHeaderValueAssertion(string headerKey)
         _headerKey = headerKey;
     }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var headers = context.Response.Headers;
+        var headers = context.HttpContext.Response.Headers;
         if (headers.ContainsKey(_headerKey))
         {
             var values = headers[_headerKey];
             var valueText = values.Select(x => "'" + x + "'").Aggregate((s1, s2) => $"{s1}, {s2}");
-            ex.Add($"Expected no value for header '{_headerKey}', but found values {valueText}");
+            context.AddFailure($"Expected no value for header '{_headerKey}', but found values {valueText}");
         }
     }
 }
diff --git a/src/Alba/Assertions/RedirectAssertion.cs b/src/Alba/Assertions/RedirectAssertion.cs
@@ -14,14 +14,14 @@ public RedirectAssertion(string expected, bool permanent)
     public string Expected { get; }
     public bool Permanent { get; }
 
-    public void Assert(Scenario scenario, HttpContext context, ScenarioAssertionException ex)
+    public void Assert(Scenario scenario, AssertionContext context)
     {
-        var location = context.Response.Headers["Location"];
+        var location = context.HttpContext.Response.Headers.Location;
         if (!string.Equals(location, Expected, StringComparison.OrdinalIgnoreCase))
         {
-            ex.Add($"Expected to be redirected to '{Expected}' but was '{location}'.");
+            context.AddFailure($"Expected to be redirected to '{Expected}' but was '{location}'.");
         }
 
-        new StatusCodeAssertion(Permanent ? 301 : 302).Assert(scenario, context, ex);
+        new StatusCodeAssertion(Permanent ? 301 : 302).Assert(scenario, context);
     }
 }