Add NotContainEquivalentOf with OccurrenceConstraint parameter for string assertions

Src/FluentAssertions/Primitives/StringAssertions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
@@ -1260,6 +1261,53 @@ public AndConstraint<TAssertions> NotContainAny(params string[] values)
         return new AndConstraint<TAssertions>((TAssertions)this);
     }
 
+    /// <summary>
+    /// Asserts that a string does not contain the specified <paramref name="unexpected"/> string,
+    /// including any leading or trailing whitespace, with the exception of the casing.
+    /// </summary>
+    /// <param name="unexpected">The string that the subject is not expected to contain.</param>
+    /// <param name="occurrenceConstraint">
+    /// A constraint specifying the amount of times a substring should be present within the test subject.
+    /// It can be created by invoking static methods Once, Twice, Thrice, or Times(int)
+    /// on the classes <see cref="Exactly"/>, <see cref="AtLeast"/>, <see cref="MoreThan"/>, <see cref="AtMost"/>, and <see cref="LessThan"/>.
+    /// For example, <see cref="Exactly.Times(int)"/> or <see cref="LessThan.Twice()"/>.
+    /// </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>
+    public AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected,
+        OccurrenceConstraint occurrenceConstraint,
+        string because = "", params object[] becauseArgs)
+    {
+        Guard.ThrowIfArgumentIsNull(occurrenceConstraint);
+
+        Execute.Assertion
+            .ForCondition(!string.IsNullOrEmpty(unexpected) && Subject != null)
+            .BecauseOf(because, becauseArgs)
+            .FailWith("Did not expect {context:string} to contain the equivalent of {0}{reason}, but found {1}.", unexpected, Subject);
+
+        bool notEquivalent;
+
+        using (var scope = new AssertionScope())
+        {
+            Subject.Should().ContainEquivalentOf(unexpected, occurrenceConstraint);
+            notEquivalent = scope.Discard().Length > 0;
+        }
+
+        var assertion = Execute.Assertion;
+        occurrenceConstraint.RegisterReportables(assertion);
+        assertion
+            .ForCondition(notEquivalent)
+            .BecauseOf(because, becauseArgs)
+            .FailWith("Did not expect {context:string} to contain the equivalent of {0} {expectedOccurrence}{reason}, but found it in {1}.", unexpected, Subject);
+
+        return new AndConstraint<TAssertions>((TAssertions)this);
+    }
+
     private static bool Contains(string actual, string expected, StringComparison comparison)
     {
         return (actual ?? string.Empty).Contains(expected ?? string.Empty, comparison);

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

@@ -2060,6 +2060,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(params string[] values) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(System.Collections.Generic.IEnumerable<string> values, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, FluentAssertions.OccurrenceConstraint occurrenceConstraint, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWith(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWithEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotMatch(string wildcardPattern, string because = "", params object[] becauseArgs) { }

Tests/Approval.Tests/ApprovedApi/FluentAssertions/net6.0.verified.txt

@@ -2144,6 +2144,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(params string[] values) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(System.Collections.Generic.IEnumerable<string> values, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, FluentAssertions.OccurrenceConstraint occurrenceConstraint, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWith(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWithEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotMatch(string wildcardPattern, string because = "", params object[] becauseArgs) { }

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

@@ -2011,6 +2011,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(params string[] values) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(System.Collections.Generic.IEnumerable<string> values, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, FluentAssertions.OccurrenceConstraint occurrenceConstraint, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWith(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWithEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotMatch(string wildcardPattern, string because = "", params object[] becauseArgs) { }

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

@@ -2060,6 +2060,7 @@ namespace FluentAssertions.Primitives
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(params string[] values) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainAny(System.Collections.Generic.IEnumerable<string> values, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
+        public FluentAssertions.AndConstraint<TAssertions> NotContainEquivalentOf(string unexpected, FluentAssertions.OccurrenceConstraint occurrenceConstraint, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWith(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotEndWithEquivalentOf(string unexpected, string because = "", params object[] becauseArgs) { }
         public FluentAssertions.AndConstraint<TAssertions> NotMatch(string wildcardPattern, string because = "", params object[] becauseArgs) { }

Tests/FluentAssertions.Specs/Primitives/StringAssertionSpecs.ContainEquivalentOf.cs

@@ -470,5 +470,24 @@ public void Should_succeed_when_asserting_string_does_not_contain_equivalent_of_
             // Assert
             act.Should().NotThrow();
         }
+
+        [Fact]
+        public void Fail_for_too_many_occurences_according_to_occurence_constraint()
+        {
+            // Act
+            Action act = () =>
+                "abc".Should().NotContainEquivalentOf("a", AtMost.Once());
+
+            // Assert
+            act.Should().Throw<XunitException>()
+                .WithMessage("Did not expect string to contain the equivalent of \"a\" at most 1 time, but found it in \"abc\".");
+        }
+
+        [Fact]
+        public void Succeed_for_correct_occurences_according_to_occurence_constraint()
+        {
+            // Act / Assert
+            "abc".Should().NotContainEquivalentOf("a", AtLeast.Twice());
+        }
     }
 }

docs/_pages/releases.md

@@ -16,6 +16,7 @@ sidebar:
 ### Improvements
 * Improve failure message for string assertions when checking for equality - [#2307](https://github.com/fluentassertions/fluentassertions/pull/2307)
 * You can mark all assertions in an assembly as custom assertions using the `[CustomAssertionsAssembly]` attribute - [#2389](https://github.com/fluentassertions/fluentassertions/pull/2389)
+* Add `NotContainEquivalentOf` with `OccurrenceConstraint` parameter for string assertions - [#2436](https://github.com/fluentassertions/fluentassertions/pull/2436)
 
 ### Fixes
 * Fixed formatting error when checking nullable `DateTimeOffset` with