fluent-assertions

Basic Value Assertions

```csharp

// Strings

wallet.Address.Should().NotBeNullOrEmpty();

blueprint.Title.Should().Be("Purchase Order");

error.Message.Should().Contain("validation");

// Numbers

blueprint.Version.Should().Be(5);

result.Count.Should().BeGreaterThan(0).And.BeLessThan(100);

// Booleans

result.IsSuccess.Should().BeTrue();

validation.IsValid.Should().BeFalse();

```

Exception Testing

```csharp

// Sync exception testing

builder.Invoking(b => b.Build())

.Should().Throw()

.WithMessage("title"); // Wildcard matching

// Async exception testing

await Assert.ThrowsAsync(async () =>

await _walletManager.CreateWalletAsync("Test", null!, "user1", "tenant1"));

```

Collection Assertions

```csharp

blueprint.Participants.Should().HaveCount(2);

blueprint.Actions.Should().NotBeEmpty();

events.Should().ContainSingle(e => e is WalletCreatedEvent);

wallets.Should().AllSatisfy(w => w.Owner.Should().Be(owner));

docket.TransactionIds.Should().ContainInOrder("tx1", "tx2", "tx3");

```

| Concept | Usage | Example |

|---------|-------|---------|

| Should() | Entry point for all assertions | value.Should().Be(expected) |

| And | Chain multiple assertions | .NotBeNull().And.HaveCount(2) |

| Which/WhoseValue | Access nested values | .ContainKey("x").WhoseValue.Should().Be("y") |

| Invoking | Test sync exceptions | obj.Invoking(x => x.Method()) |

| Awaiting | Test async exceptions | obj.Awaiting(x => x.MethodAsync()) |

Object Property Assertions

```csharp

wallet.Should().NotBeNull();

wallet.Name.Should().Be("Test Wallet");

wallet.Status.Should().Be(WalletStatus.Active);

wallet.Metadata.Should().ContainKey("environment").WhoseValue.Should().Be("production");

```

Time-Based Assertions

```csharp

docket.TimeStamp.Should().BeCloseTo(DateTime.UtcNow, TimeSpan.FromSeconds(1));

blueprint.UpdatedAt.Should().BeOnOrAfter(beforeBuild).And.BeOnOrBefore(afterBuild);

```

Validation Result Assertions

```csharp

result.Validation.IsValid.Should().BeTrue();

result.Errors.Should().BeEmpty();

// Or for failures

result.Success.Should().BeFalse();

result.Validation.Errors.Should().NotBeEmpty();

result.Errors.Should().Contain(e => e.Contains("validation"));

```

• [patterns](references/patterns.md)
• [workflows](references/workflows.md)

• See the xunit skill for test framework patterns
• See the moq skill for mocking dependencies in tests

> Fetch latest FluentAssertions documentation with Context7.

How to use Context7:

1. Use mcp__context7__resolve-library-id to search for "fluent-assertions"
2. Prefer website documentation (IDs starting with /websites/) over source code repositories when available
3. Query with mcp__context7__query-docs using the resolved library ID

Library ID: /fluentassertions/fluentassertions

Recommended Queries:

• "FluentAssertions basic assertions Should Be"
• "FluentAssertions collection assertions HaveCount Contain"
• "FluentAssertions exception testing ThrowAsync"
• "FluentAssertions object equivalence BeEquivalentTo"