Added AllSatisfy for asserting all items in a collection satisfy an…

… inspector (#1790)

Src/FluentAssertions/Collections/GenericCollectionAssertions.cs

@@ -2671,6 +2671,66 @@ public AndConstraint<TAssertions> OnlyHaveUniqueItems(string because = "", param
             return new AndConstraint<TAssertions>((TAssertions)this);
         }
 
+        /// <summary>
+        /// Asserts that a collection contains only items which meet
+        /// the criteria provided by the inspector.
+        /// </summary>
+        /// <param name="expected">
+        /// The element inspector, which inspects each element in turn.
+        /// </param>
+        /// <param name="because">
+        /// A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
+        /// is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
+        /// </param>
+        /// <param name="becauseArgs">
+        /// Zero or more objects to format using the placeholders in <paramref name="because"/>.
+        /// </param>
+        /// <exception cref="ArgumentNullException"><paramref name="expected"/> is <c>null</c>.</exception>
+        public AndConstraint<TAssertions> AllSatisfy(Action<T> expected, string because = "", params object[] becauseArgs)
+        {
+            Guard.ThrowIfArgumentIsNull(expected, nameof(expected), "Cannot verify against a <null> inspector");
+
+            bool success = Execute.Assertion
+                .BecauseOf(because, becauseArgs)
+                .WithExpectation("Expected {context:collection} to contain only items satisfying the inspector{reason}, ")
+                .Given(() => Subject)
+                .ForCondition(subject => subject is not null)
+                .FailWith("but collection is <null>.")
+                .Then
+                .ForCondition(subject => subject.Any())
+                .FailWith("but collection is empty.")
+                .Then
+                .ClearExpectation();
+
+            if (success)
+            {
+                string[] failuresFromInspectors;
+
+                using (CallerIdentifier.OverrideStackSearchUsingCurrentScope())
+                {
+                    var elementInspectors = Subject.Select(_ => expected);
+                    failuresFromInspectors = CollectFailuresFromInspectors(elementInspectors);
+                }
+
+                if (failuresFromInspectors.Any())
+                {
+                    string failureMessage = Environment.NewLine
+                        + string.Join(Environment.NewLine, failuresFromInspectors.Select(x => x.IndentLines()));
+
+                    Execute.Assertion
+                        .BecauseOf(because, becauseArgs)
+                        .WithExpectation("Expected {context:collection} to contain only items satisfying the inspector{reason}:")
+                        .FailWithPreFormatted(failureMessage)
+                        .Then
+                        .ClearExpectation();
+                }
+
+                return new AndConstraint<TAssertions>((TAssertions)this);
+            }
+
+            return new AndConstraint<TAssertions>((TAssertions)this);
+        }
+
         /// <summary>
         /// Asserts that a collection contains exactly a given number of elements, which meet
         /// the criteria provided by the element inspectors.

Tests/Approval.Tests/ApprovedApi/FluentAssertions/net47.verified.txt

@@ -392,6 +392,7 @@ namespace FluentAssertions.Collections
         public FluentAssertions.AndConstraint<TAssertions> AllBeEquivalentTo<TExpectation>(TExpectation expectation, System.Func<FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>, FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>> config, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> AllBeOfType(System.Type expectedType, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndWhichConstraint<TAssertions, System.Collections.Generic.IEnumerable<TExpectation>> AllBeOfType<TExpectation>(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> AllSatisfy(System.Action<T> expected, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionEndsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actual, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionStartsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actualItems, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertSubjectEquality<TExpectation>(System.Collections.Generic.IEnumerable<TExpectation> expectation, System.Func<T, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netcoreapp2.1.verified.txt

@@ -392,6 +392,7 @@ namespace FluentAssertions.Collections
         public FluentAssertions.AndConstraint<TAssertions> AllBeEquivalentTo<TExpectation>(TExpectation expectation, System.Func<FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>, FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>> config, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> AllBeOfType(System.Type expectedType, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndWhichConstraint<TAssertions, System.Collections.Generic.IEnumerable<TExpectation>> AllBeOfType<TExpectation>(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> AllSatisfy(System.Action<T> expected, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionEndsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actual, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionStartsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actualItems, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertSubjectEquality<TExpectation>(System.Collections.Generic.IEnumerable<TExpectation> expectation, System.Func<T, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netcoreapp3.0.verified.txt

@@ -392,6 +392,7 @@ namespace FluentAssertions.Collections
         public FluentAssertions.AndConstraint<TAssertions> AllBeEquivalentTo<TExpectation>(TExpectation expectation, System.Func<FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>, FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>> config, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> AllBeOfType(System.Type expectedType, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndWhichConstraint<TAssertions, System.Collections.Generic.IEnumerable<TExpectation>> AllBeOfType<TExpectation>(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> AllSatisfy(System.Action<T> expected, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionEndsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actual, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionStartsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actualItems, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertSubjectEquality<TExpectation>(System.Collections.Generic.IEnumerable<TExpectation> expectation, System.Func<T, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netstandard2.0.verified.txt

@@ -385,6 +385,7 @@ namespace FluentAssertions.Collections
         public FluentAssertions.AndConstraint<TAssertions> AllBeEquivalentTo<TExpectation>(TExpectation expectation, System.Func<FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>, FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>> config, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> AllBeOfType(System.Type expectedType, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndWhichConstraint<TAssertions, System.Collections.Generic.IEnumerable<TExpectation>> AllBeOfType<TExpectation>(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> AllSatisfy(System.Action<T> expected, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionEndsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actual, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionStartsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actualItems, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertSubjectEquality<TExpectation>(System.Collections.Generic.IEnumerable<TExpectation> expectation, System.Func<T, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/netstandard2.1.verified.txt

@@ -392,6 +392,7 @@ namespace FluentAssertions.Collections
         public FluentAssertions.AndConstraint<TAssertions> AllBeEquivalentTo<TExpectation>(TExpectation expectation, System.Func<FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>, FluentAssertions.Equivalency.EquivalencyAssertionOptions<TExpectation>> config, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> AllBeOfType(System.Type expectedType, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndWhichConstraint<TAssertions, System.Collections.Generic.IEnumerable<TExpectation>> AllBeOfType<TExpectation>(string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> AllSatisfy(System.Action<T> expected, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionEndsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actual, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertCollectionStartsWith<TActual, TExpectation>(System.Collections.Generic.IEnumerable<TActual> actualItems, System.Collections.Generic.ICollection<TExpectation> expected, System.Func<TActual, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }
         protected void AssertSubjectEquality<TExpectation>(System.Collections.Generic.IEnumerable<TExpectation> expectation, System.Func<T, TExpectation, bool> equalityComparison, string because = "", params object[] becauseArgs) { }

Tests/FluentAssertions.Specs/Collections/CollectionAssertionSpecs.AllSatisfy.cs

@@ -0,0 +1,133 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using FluentAssertions.Execution;
+using Xunit;
+using Xunit.Sdk;
+
+namespace FluentAssertions.Specs.Collections
+{
+    /// <content>
+    /// The AllSatisfy specs.
+    /// </content>
+    public partial class CollectionAssertionSpecs
+    {
+        public class AllSatisfy
+        {
+            [Fact]
+            public void A_null_inspector_should_throw()
+            {
+                // Arrange
+                IEnumerable<int> collection = new[] { 1, 2 };
+
+                // Act
+                Action act = () => collection.Should().AllSatisfy(null);
+
+                // Assert
+                act.Should()
+                    .Throw<ArgumentException>()
+                    .WithMessage("Cannot verify against a <null> inspector*");
+            }
+
+            [Fact]
+            public void A_null_collection_should_throw()
+            {
+                // Arrange
+                IEnumerable<int> collection = null;
+
+                // Act
+                Action act = () =>
+                {
+                    using var _ = new AssertionScope();
+                    collection.Should().AllSatisfy(x => x.Should().Be(1), "because we want to test the failure {0}", "message");
+                };
+
+                // Assert
+                act.Should()
+                    .Throw<XunitException>()
+                    .WithMessage(
+                        "Expected collection to contain only items satisfying the inspector because we want to test the failure message, but collection is <null>.");
+            }
+
+            [Fact]
+            public void An_empty_collection_should_throw()
+            {
+                // Arrange
+                var collection = Enumerable.Empty<int>();
+
+                // Act
+                Action act = ()
+                    => collection.Should()
+                        .AllSatisfy(x => x.Should().Be(1), "because we want to test the failure {0}", "message");
+
+                // Assert
+                act.Should()
+                    .Throw<XunitException>()
+                    .WithMessage(
+                        "Expected collection to contain only items satisfying the inspector because we want to test the failure message, but collection is empty.");
+            }
+
+            [Fact]
+            public void All_items_satisfying_inspector_should_succeed()
+            {
+                // Arrange
+                var collection = new[] { new Customer { Age = 21, Name = "John" }, new Customer { Age = 21, Name = "Jane" } };
+
+                // Act / Assert
+                collection.Should().AllSatisfy(x => x.Age.Should().Be(21));
+            }
+
+            [Fact]
+            public void Any_items_not_satisfying_inspector_should_throw()
+            {
+                // Arrange
+                var customers = new[]
+                {
+                    new CustomerWithItems { Age = 21, Items = new[] { 1, 2 } },
+                    new CustomerWithItems { Age = 22, Items = new[] { 3 } }
+                };
+
+                // Act
+                Action act = () => customers.Should()
+                    .AllSatisfy(
+                        customer =>
+                        {
+                            customer.Age.Should().BeLessThan(21);
+                            customer.Items.Should()
+                                .AllSatisfy(item => item.Should().Be(3));
+                        },
+                        "because we want to test {0}",
+                        "nested assertions");
+
+                // Assert
+                act.Should()
+                    .Throw<XunitException>()
+                    .WithMessage(
+                        @"Expected customers to contain only items satisfying the inspector because we want to test nested assertions:
+*At index 0:
+*Expected customer.Age to be less than 21, but found 21
+*Expected customer.Items to contain only items satisfying the inspector:
+*At index 0:
+*Expected item to be 3, but found 1
+*At index 1:
+*Expected item to be 3, but found 2
+*At index 1:
+*Expected customer.Age to be less than 21, but found 22"
+                        );
+            }
+
+            [Fact]
+            public void Inspector_message_that_is_not_reformatable_should_not_throw()
+            {
+                // Arrange
+                byte[][] subject = { new byte[] { 1 } };
+
+                // Act
+                Action act = () => subject.Should().AllSatisfy(e => e.Should().BeEquivalentTo(new byte[] { 2, 3, 4 }));
+
+                // Assert
+                act.Should().NotThrow<FormatException>();
+            }
+        }
+    }
+}

Tests/FluentAssertions.Specs/Collections/GenericCollectionAssertionOfStringSpecs.AllSatisfy.cs

@@ -0,0 +1,44 @@
+using System;
+using Xunit;
+using Xunit.Sdk;
+
+namespace FluentAssertions.Specs.Collections
+{
+    public partial class GenericCollectionAssertionOfStringSpecs
+    {
+        public class AllSatisfy
+        {
+            [Fact]
+            public void All_items_satisfying_inspector_should_succeed()
+            {
+                // Arrange
+                string[] collection = new[] { "John", "John" };
+
+                // Act / Assert
+                collection.Should().AllSatisfy(value => value.Should().Be("John"));
+            }
+
+            [Fact]
+            public void Any_items_not_satisfying_inspector_should_throw()
+            {
+                // Arrange
+                string[] collection = new[] { "Jack", "Jessica" };
+
+                // Act
+                Action act = () => collection.Should()
+                    .AllSatisfy(
+                        value => value.Should().Be("John"),
+                        "because we want to test the failure {0}",
+                        "message");
+
+                // Assert
+                act.Should()
+                    .Throw<XunitException>()
+                    .WithMessage(
+                        "Expected collection to contain only items satisfying the inspector because we want to test the failure message:"
+                        + "*John*Jack"
+                        + "*John*Jessica*");
+            }
+        }
+    }
+}

Tests/FluentAssertions.Specs/Collections/GenericCollectionAssertionOfStringSpecs.cs

@@ -9,7 +9,7 @@
 
 namespace FluentAssertions.Specs.Collections
 {
-    public class GenericCollectionAssertionOfStringSpecs
+    public partial class GenericCollectionAssertionOfStringSpecs
     {
         [Fact]
         public void Should_fail_when_asserting_collection_has_a_count_that_is_different_from_the_number_of_items()

docs/_pages/collections.md

@@ -190,6 +190,22 @@ collection.Should().SatisfyRespectively(
     });
 ```
 
+If you need to perform the same assertion on all elements of a collection:
+
+```csharp
+var collection = new []
+{
+    new { Id = 1, Name = "John", Attributes = new string[] { } },
+    new { Id = 2, Name = "Jane", Attributes = new string[] { "attr" } }
+};
+collection.Should().AllSatisfy(x =>
+{
+    x.Id.Should().BePositive();
+    x.Name.Should().StartWith("J");
+    x.Attributes.Should().NotBeNull();
+});
+```
+
 If you need to perform individual assertions on all elements of a collection without setting expectation about the order of elements:
 
 ```csharp

docs/_pages/releases.md

@@ -10,6 +10,7 @@ sidebar:
 ## Unreleased
 
 ### What's New
+* Added `AllSatisfy` for asserting all items in a collection satisfy an inspector - [#1790](https://github.com/fluentassertions/fluentassertions/pull/1790)
 * Added `WithMapping` option to `BeEquivalentTo` to map members with different names between the subject and expectation - [#1742](https://github.com/fluentassertions/fluentassertions/pull/1742)
 
 ### Fixes