From ac892b64da73c9ab5271ed1a98a349e87708d48c Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Fri, 8 Aug 2025 12:09:38 -0500
Subject: [PATCH 1/7] Emit a warning if a display name string is empty

Fixes rdar://157603034
---
 Sources/TestingMacros/CMakeLists.txt          |  1 +
 .../StringLiteralExprSyntaxAdditions.swift    | 30 +++++++++++++++++++
 .../Support/AttributeDiscovery.swift          |  8 +++++
 .../Support/DiagnosticMessage.swift           | 16 ++++++++++
 .../TestDeclarationMacroTests.swift           |  8 +++++
 5 files changed, 63 insertions(+)
 create mode 100644 Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift

diff --git a/Sources/TestingMacros/CMakeLists.txt b/Sources/TestingMacros/CMakeLists.txt
index effa782a9..64f825f5a 100644
--- a/Sources/TestingMacros/CMakeLists.txt
+++ b/Sources/TestingMacros/CMakeLists.txt
@@ -90,6 +90,7 @@ target_sources(TestingMacros PRIVATE
   Support/Additions/FunctionDeclSyntaxAdditions.swift
   Support/Additions/IntegerLiteralExprSyntaxAdditions.swift
   Support/Additions/MacroExpansionContextAdditions.swift
+  Support/Additions/StringLiteralExprSyntaxAdditions.swift
   Support/Additions/TokenSyntaxAdditions.swift
   Support/Additions/TriviaPieceAdditions.swift
   Support/Additions/TypeSyntaxProtocolAdditions.swift
diff --git a/Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift b/Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift
new file mode 100644
index 000000000..d11d7ad54
--- /dev/null
+++ b/Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift
@@ -0,0 +1,30 @@
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+//
+
+import SwiftSyntax
+
+extension StringLiteralExprSyntax {
+  /// Whether or not this string literal expression is completely empty.
+  ///
+  /// The value of this property is `false` even if the literal contains one or
+  /// more interpolation segments whose evaluated expressions are an empty
+  /// string. The value is only `true` if this string literal contains only one
+  /// empty string segment.
+  var isEmptyLiteral: Bool {
+    guard segments.count == 1,
+          case let .stringSegment(stringSegment) = segments.first,
+          case let .stringSegment(text) = stringSegment.content.tokenKind
+    else {
+      return false
+    }
+
+    return text.isEmpty
+  }
+}
diff --git a/Sources/TestingMacros/Support/AttributeDiscovery.swift b/Sources/TestingMacros/Support/AttributeDiscovery.swift
index 3d95df294..afefd259e 100644
--- a/Sources/TestingMacros/Support/AttributeDiscovery.swift
+++ b/Sources/TestingMacros/Support/AttributeDiscovery.swift
@@ -149,6 +149,14 @@ struct AttributeInfo {
       }
     }
 
+    // If there was a display name but it's completely empty, emit a warning
+    // diagnostic since this can cause confusion isn't generally recommended.
+    // Note that this is only possible for string literal display names; the
+    // compiler enforces that raw identifiers must be non-empty.
+    if let displayName, displayName.isEmptyLiteral {
+      context.diagnose(.emptyDisplayName(displayName))
+    }
+
     // Remove leading "Self." expressions from the arguments of the attribute.
     // See _SelfRemover for more information. Rewriting a syntax tree discards
     // location information from the copy, so only invoke the rewriter if the
diff --git a/Sources/TestingMacros/Support/DiagnosticMessage.swift b/Sources/TestingMacros/Support/DiagnosticMessage.swift
index 80c3d9e1f..9aa4acdc2 100644
--- a/Sources/TestingMacros/Support/DiagnosticMessage.swift
+++ b/Sources/TestingMacros/Support/DiagnosticMessage.swift
@@ -643,6 +643,22 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
     )
   }
 
+  /// Create a diagnostic message stating that a string literal expression
+  /// passed as the display name to a `@Test` or `@Suite` attribute is empty
+  /// but should not be.
+  ///
+  /// - Parameters:
+  ///   - displayNameExpr: The display name string literal expression.
+  ///
+  /// - Returns: A diagnostic message.
+  static func emptyDisplayName(_ displayNameExpr: StringLiteralExprSyntax) -> Self {
+    Self(
+      syntax: Syntax(displayNameExpr),
+      message: "Display name string should not be empty",
+      severity: .warning
+    )
+  }
+
   /// Create a diagnostic message stating that a declaration has two display
   /// names.
   ///
diff --git a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
index 47e2b5112..f36c7d3b3 100644
--- a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
+++ b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
@@ -304,6 +304,14 @@ struct TestDeclarationMacroTests {
       // .serialized on a non-parameterized test function
       "@Test(.serialized) func f() {}":
         "Trait '.serialized' has no effect when used with a non-parameterized test function",
+
+      // empty display name string literal
+      #"@Test("") func f() {}"#:
+        "Display name string should not be empty",
+      ##"@Test(#""#) func f() {}"##:
+        "Display name string should not be empty",
+      #"@Suite("") struct S {}"#:
+        "Display name string should not be empty",
     ]
   )
   func apiMisuseWarnings(input: String, expectedMessage: String) throws {

From ba7214d5bd9d4fc6a06921a7edc765cd6f7d4c58 Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Fri, 8 Aug 2025 22:04:04 -0500
Subject: [PATCH 2/7] Use representedLiteralValue instead

---
 Sources/TestingMacros/CMakeLists.txt          |  1 -
 .../StringLiteralExprSyntaxAdditions.swift    | 30 -------------------
 .../Support/AttributeDiscovery.swift          |  3 +-
 3 files changed, 2 insertions(+), 32 deletions(-)
 delete mode 100644 Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift

diff --git a/Sources/TestingMacros/CMakeLists.txt b/Sources/TestingMacros/CMakeLists.txt
index 64f825f5a..effa782a9 100644
--- a/Sources/TestingMacros/CMakeLists.txt
+++ b/Sources/TestingMacros/CMakeLists.txt
@@ -90,7 +90,6 @@ target_sources(TestingMacros PRIVATE
   Support/Additions/FunctionDeclSyntaxAdditions.swift
   Support/Additions/IntegerLiteralExprSyntaxAdditions.swift
   Support/Additions/MacroExpansionContextAdditions.swift
-  Support/Additions/StringLiteralExprSyntaxAdditions.swift
   Support/Additions/TokenSyntaxAdditions.swift
   Support/Additions/TriviaPieceAdditions.swift
   Support/Additions/TypeSyntaxProtocolAdditions.swift
diff --git a/Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift b/Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift
deleted file mode 100644
index d11d7ad54..000000000
--- a/Sources/TestingMacros/Support/Additions/StringLiteralExprSyntaxAdditions.swift
+++ /dev/null
@@ -1,30 +0,0 @@
-//
-// This source file is part of the Swift.org open source project
-//
-// Copyright (c) 2025 Apple Inc. and the Swift project authors
-// Licensed under Apache License v2.0 with Runtime Library Exception
-//
-// See https://swift.org/LICENSE.txt for license information
-// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
-//
-
-import SwiftSyntax
-
-extension StringLiteralExprSyntax {
-  /// Whether or not this string literal expression is completely empty.
-  ///
-  /// The value of this property is `false` even if the literal contains one or
-  /// more interpolation segments whose evaluated expressions are an empty
-  /// string. The value is only `true` if this string literal contains only one
-  /// empty string segment.
-  var isEmptyLiteral: Bool {
-    guard segments.count == 1,
-          case let .stringSegment(stringSegment) = segments.first,
-          case let .stringSegment(text) = stringSegment.content.tokenKind
-    else {
-      return false
-    }
-
-    return text.isEmpty
-  }
-}
diff --git a/Sources/TestingMacros/Support/AttributeDiscovery.swift b/Sources/TestingMacros/Support/AttributeDiscovery.swift
index afefd259e..19a660a47 100644
--- a/Sources/TestingMacros/Support/AttributeDiscovery.swift
+++ b/Sources/TestingMacros/Support/AttributeDiscovery.swift
@@ -11,6 +11,7 @@
 import SwiftSyntax
 import SwiftSyntaxBuilder
 import SwiftSyntaxMacros
+import SwiftParser
 
 /// A syntax rewriter that removes leading `Self.` tokens from member access
 /// expressions in a syntax tree.
@@ -153,7 +154,7 @@ struct AttributeInfo {
     // diagnostic since this can cause confusion isn't generally recommended.
     // Note that this is only possible for string literal display names; the
     // compiler enforces that raw identifiers must be non-empty.
-    if let displayName, displayName.isEmptyLiteral {
+    if let displayName, displayName.representedLiteralValue?.isEmpty == true {
       context.diagnose(.emptyDisplayName(displayName))
     }
 

From 91b29e096ce09f79e66e8620811802801a0dde55 Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Tue, 12 Aug 2025 11:32:19 -0500
Subject: [PATCH 3/7] Add removal fix-it

---
 .../Support/AttributeDiscovery.swift              |  4 ++--
 .../TestingMacros/Support/DiagnosticMessage.swift | 15 +++++++++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/Sources/TestingMacros/Support/AttributeDiscovery.swift b/Sources/TestingMacros/Support/AttributeDiscovery.swift
index 19a660a47..cdbff7d54 100644
--- a/Sources/TestingMacros/Support/AttributeDiscovery.swift
+++ b/Sources/TestingMacros/Support/AttributeDiscovery.swift
@@ -154,8 +154,8 @@ struct AttributeInfo {
     // diagnostic since this can cause confusion isn't generally recommended.
     // Note that this is only possible for string literal display names; the
     // compiler enforces that raw identifiers must be non-empty.
-    if let displayName, displayName.representedLiteralValue?.isEmpty == true {
-      context.diagnose(.emptyDisplayName(displayName))
+    if let displayName, let displayNameArgument, displayName.representedLiteralValue?.isEmpty == true {
+      context.diagnose(.emptyDisplayName(displayName, fromArgument: displayNameArgument))
     }
 
     // Remove leading "Self." expressions from the arguments of the attribute.
diff --git a/Sources/TestingMacros/Support/DiagnosticMessage.swift b/Sources/TestingMacros/Support/DiagnosticMessage.swift
index 9aa4acdc2..564b19abb 100644
--- a/Sources/TestingMacros/Support/DiagnosticMessage.swift
+++ b/Sources/TestingMacros/Support/DiagnosticMessage.swift
@@ -649,13 +649,24 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
   ///
   /// - Parameters:
   ///   - displayNameExpr: The display name string literal expression.
+  ///   - argumentContainingDisplayName: The argument node containing the node
+  ///     `displayNameExpr`.
   ///
   /// - Returns: A diagnostic message.
-  static func emptyDisplayName(_ displayNameExpr: StringLiteralExprSyntax) -> Self {
+  static func emptyDisplayName(
+    _ displayNameExpr: StringLiteralExprSyntax,
+    fromArgument argumentContainingDisplayName: LabeledExprListSyntax.Element
+  ) -> Self {
     Self(
       syntax: Syntax(displayNameExpr),
       message: "Display name string should not be empty",
-      severity: .warning
+      severity: .warning,
+      fixIts: [
+        FixIt(
+          message: MacroExpansionFixItMessage("Remove '\(displayNameExpr.representedLiteralValue!)'"),
+          changes: [.replace(oldNode: Syntax(argumentContainingDisplayName), newNode: Syntax("" as ExprSyntax))]
+        ),
+      ]
     )
   }
 

From 4b48d71467b27b87e2029dcc3f6a24c71639608b Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Tue, 12 Aug 2025 11:43:17 -0500
Subject: [PATCH 4/7] Improve diagnostic message for consistency

---
 .../TestingMacros/Support/AttributeDiscovery.swift   |  6 ++++--
 .../TestingMacros/Support/DiagnosticMessage.swift    | 12 ++++++++----
 .../TestDeclarationMacroTests.swift                  |  6 +++---
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/Sources/TestingMacros/Support/AttributeDiscovery.swift b/Sources/TestingMacros/Support/AttributeDiscovery.swift
index cdbff7d54..9d7f70916 100644
--- a/Sources/TestingMacros/Support/AttributeDiscovery.swift
+++ b/Sources/TestingMacros/Support/AttributeDiscovery.swift
@@ -154,8 +154,10 @@ struct AttributeInfo {
     // diagnostic since this can cause confusion isn't generally recommended.
     // Note that this is only possible for string literal display names; the
     // compiler enforces that raw identifiers must be non-empty.
-    if let displayName, let displayNameArgument, displayName.representedLiteralValue?.isEmpty == true {
-      context.diagnose(.emptyDisplayName(displayName, fromArgument: displayNameArgument))
+    if let namedDecl = declaration.asProtocol((any NamedDeclSyntax).self),
+       let displayName, let displayNameArgument,
+        displayName.representedLiteralValue?.isEmpty == true {
+      context.diagnose(.declaration(namedDecl, hasEmptyDisplayName: displayName, fromArgument: displayNameArgument, using: attribute))
     }
 
     // Remove leading "Self." expressions from the arguments of the attribute.
diff --git a/Sources/TestingMacros/Support/DiagnosticMessage.swift b/Sources/TestingMacros/Support/DiagnosticMessage.swift
index 564b19abb..64a4a57ca 100644
--- a/Sources/TestingMacros/Support/DiagnosticMessage.swift
+++ b/Sources/TestingMacros/Support/DiagnosticMessage.swift
@@ -648,18 +648,22 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
   /// but should not be.
   ///
   /// - Parameters:
+  ///   - decl: The declaration that has an empty display name.
   ///   - displayNameExpr: The display name string literal expression.
   ///   - argumentContainingDisplayName: The argument node containing the node
   ///     `displayNameExpr`.
+  ///   - attribute: The `@Test` or `@Suite` attribute.
   ///
   /// - Returns: A diagnostic message.
-  static func emptyDisplayName(
-    _ displayNameExpr: StringLiteralExprSyntax,
-    fromArgument argumentContainingDisplayName: LabeledExprListSyntax.Element
+  static func declaration(
+    _ decl: some NamedDeclSyntax,
+    hasEmptyDisplayName displayNameExpr: StringLiteralExprSyntax,
+    fromArgument argumentContainingDisplayName: LabeledExprListSyntax.Element,
+    using attribute: AttributeSyntax
   ) -> Self {
     Self(
       syntax: Syntax(displayNameExpr),
-      message: "Display name string should not be empty",
+      message: "Attribute \(_macroName(attribute)) specifies an empty display name for \(_kindString(for: decl))",
       severity: .warning,
       fixIts: [
         FixIt(
diff --git a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
index f36c7d3b3..13fcd4f8d 100644
--- a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
+++ b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
@@ -307,11 +307,11 @@ struct TestDeclarationMacroTests {
 
       // empty display name string literal
       #"@Test("") func f() {}"#:
-        "Display name string should not be empty",
+        "Attribute 'Test' specifies an empty display name for function",
       ##"@Test(#""#) func f() {}"##:
-        "Display name string should not be empty",
+        "Attribute 'Test' specifies an empty display name for function",
       #"@Suite("") struct S {}"#:
-        "Display name string should not be empty",
+        "Attribute 'Suite' specifies an empty display name for structure",
     ]
   )
   func apiMisuseWarnings(input: String, expectedMessage: String) throws {

From 8b2cdf27b164f49331fbb76558e23bc387789848 Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Tue, 12 Aug 2025 15:47:03 -0500
Subject: [PATCH 5/7] Improve phrasing

---
 Sources/TestingMacros/Support/DiagnosticMessage.swift    | 4 ++--
 Tests/TestingMacrosTests/TestDeclarationMacroTests.swift | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Sources/TestingMacros/Support/DiagnosticMessage.swift b/Sources/TestingMacros/Support/DiagnosticMessage.swift
index 64a4a57ca..eccdf5422 100644
--- a/Sources/TestingMacros/Support/DiagnosticMessage.swift
+++ b/Sources/TestingMacros/Support/DiagnosticMessage.swift
@@ -663,11 +663,11 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
   ) -> Self {
     Self(
       syntax: Syntax(displayNameExpr),
-      message: "Attribute \(_macroName(attribute)) specifies an empty display name for \(_kindString(for: decl))",
+      message: "Attribute \(_macroName(attribute)) specifies an empty display name for this \(_kindString(for: decl))",
       severity: .warning,
       fixIts: [
         FixIt(
-          message: MacroExpansionFixItMessage("Remove '\(displayNameExpr.representedLiteralValue!)'"),
+          message: MacroExpansionFixItMessage("Remove display name argument"),
           changes: [.replace(oldNode: Syntax(argumentContainingDisplayName), newNode: Syntax("" as ExprSyntax))]
         ),
       ]
diff --git a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
index 13fcd4f8d..5fe5a6fde 100644
--- a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
+++ b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
@@ -307,11 +307,11 @@ struct TestDeclarationMacroTests {
 
       // empty display name string literal
       #"@Test("") func f() {}"#:
-        "Attribute 'Test' specifies an empty display name for function",
+        "Attribute 'Test' specifies an empty display name for this function",
       ##"@Test(#""#) func f() {}"##:
-        "Attribute 'Test' specifies an empty display name for function",
+        "Attribute 'Test' specifies an empty display name for this function",
       #"@Suite("") struct S {}"#:
-        "Attribute 'Suite' specifies an empty display name for structure",
+        "Attribute 'Suite' specifies an empty display name for this structure",
     ]
   )
   func apiMisuseWarnings(input: String, expectedMessage: String) throws {

From cb45a57452976282767117e9781392da30f012ef Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Wed, 13 Aug 2025 16:21:53 -0500
Subject: [PATCH 6/7] Add fix-it which fills in the display name

---
 ...EditorPlaceholderExprSyntaxAdditions.swift | 31 +++++++++++++++++--
 .../Support/DiagnosticMessage.swift           |  4 +++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/Sources/TestingMacros/Support/Additions/EditorPlaceholderExprSyntaxAdditions.swift b/Sources/TestingMacros/Support/Additions/EditorPlaceholderExprSyntaxAdditions.swift
index 9a0d31ab3..360b5260e 100644
--- a/Sources/TestingMacros/Support/Additions/EditorPlaceholderExprSyntaxAdditions.swift
+++ b/Sources/TestingMacros/Support/Additions/EditorPlaceholderExprSyntaxAdditions.swift
@@ -9,6 +9,7 @@
 //
 
 import SwiftSyntax
+import SwiftSyntaxBuilder
 
 extension EditorPlaceholderExprSyntax {
   /// Initialize an instance of this type with the given placeholder string and
@@ -39,7 +40,7 @@ extension EditorPlaceholderExprSyntax {
 
     // Manually concatenate the string to avoid it being interpreted as a
     // placeholder when editing this file.
-    self.init(placeholder: .identifier("<#\(placeholderContent)#" + ">"))
+    self.init(placeholder: .identifier(_editorPlaceholder(containing: placeholderContent)))
   }
 
   /// Initialize an instance of this type with the given type, using that as the
@@ -62,6 +63,32 @@ extension TypeSyntax {
   ///
   /// - Returns: A new `TypeSyntax` instance representing a placeholder.
   static func placeholder(_ placeholder: String) -> Self {
-    return Self(IdentifierTypeSyntax(name: .identifier("<#\(placeholder)#" + ">")))
+    Self(IdentifierTypeSyntax(name: .identifier(_editorPlaceholder(containing: placeholder))))
   }
 }
+
+extension StringLiteralExprSyntax {
+  /// Construct a string literal expression syntax node containing an editor
+  /// placeholder string.
+  ///
+  /// - Parameters
+  ///   - placeholder: The placeholder string, not including surrounding angle
+  ///     brackets or pound characters.
+  init(placeholder: String) {
+    self.init(content: _editorPlaceholder(containing: placeholder))
+  }
+}
+
+/// Format a source editor placeholder string with the specified content.
+///
+/// - Parameters:
+///   - content: The placeholder string, not including surrounding angle
+///     brackets or pound characters
+///
+/// - Returns: A fully-formatted formatted editor placeholder string, including
+///   necessary surrounding punctuation.
+private func _editorPlaceholder(containing content: String) -> String {
+  // Manually concatenate the string to avoid it being interpreted as a
+  // placeholder when editing this file.
+  "<#\(content)#" + ">"
+}
diff --git a/Sources/TestingMacros/Support/DiagnosticMessage.swift b/Sources/TestingMacros/Support/DiagnosticMessage.swift
index eccdf5422..212e561ce 100644
--- a/Sources/TestingMacros/Support/DiagnosticMessage.swift
+++ b/Sources/TestingMacros/Support/DiagnosticMessage.swift
@@ -670,6 +670,10 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
           message: MacroExpansionFixItMessage("Remove display name argument"),
           changes: [.replace(oldNode: Syntax(argumentContainingDisplayName), newNode: Syntax("" as ExprSyntax))]
         ),
+        FixIt(
+          message: MacroExpansionFixItMessage("Add display name"),
+          changes: [.replace(oldNode: Syntax(argumentContainingDisplayName), newNode: Syntax(StringLiteralExprSyntax(placeholder: "display name")))]
+        ),
       ]
     )
   }

From 8ab1a4cd272a702f1a8092e7917af4c6f5b13c55 Mon Sep 17 00:00:00 2001
From: Stuart Montgomery <smontgomery@apple.com>
Date: Wed, 13 Aug 2025 16:25:47 -0500
Subject: [PATCH 7/7] Switch warning severity to error

---
 .../Support/AttributeDiscovery.swift             |  8 ++++----
 .../Support/DiagnosticMessage.swift              |  2 +-
 .../TestDeclarationMacroTests.swift              | 16 ++++++++--------
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/Sources/TestingMacros/Support/AttributeDiscovery.swift b/Sources/TestingMacros/Support/AttributeDiscovery.swift
index 9d7f70916..fdf4b7e93 100644
--- a/Sources/TestingMacros/Support/AttributeDiscovery.swift
+++ b/Sources/TestingMacros/Support/AttributeDiscovery.swift
@@ -150,10 +150,10 @@ struct AttributeInfo {
       }
     }
 
-    // If there was a display name but it's completely empty, emit a warning
-    // diagnostic since this can cause confusion isn't generally recommended.
-    // Note that this is only possible for string literal display names; the
-    // compiler enforces that raw identifiers must be non-empty.
+    // If there was a display name but it's completely empty, emit a diagnostic
+    // since this can cause confusion isn't generally recommended. Note that
+    // this is only possible for string literal display names; the compiler
+    // enforces that raw identifiers must be non-empty.
     if let namedDecl = declaration.asProtocol((any NamedDeclSyntax).self),
        let displayName, let displayNameArgument,
         displayName.representedLiteralValue?.isEmpty == true {
diff --git a/Sources/TestingMacros/Support/DiagnosticMessage.swift b/Sources/TestingMacros/Support/DiagnosticMessage.swift
index 212e561ce..7d7ee1f31 100644
--- a/Sources/TestingMacros/Support/DiagnosticMessage.swift
+++ b/Sources/TestingMacros/Support/DiagnosticMessage.swift
@@ -664,7 +664,7 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
     Self(
       syntax: Syntax(displayNameExpr),
       message: "Attribute \(_macroName(attribute)) specifies an empty display name for this \(_kindString(for: decl))",
-      severity: .warning,
+      severity: .error,
       fixIts: [
         FixIt(
           message: MacroExpansionFixItMessage("Remove display name argument"),
diff --git a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
index 5fe5a6fde..9ac9c6264 100644
--- a/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
+++ b/Tests/TestingMacrosTests/TestDeclarationMacroTests.swift
@@ -149,6 +149,14 @@ struct TestDeclarationMacroTests {
         "Attribute 'Test' cannot be applied to a function within structure 'S' because its conformance to 'Escapable' has been suppressed",
       "struct S: ~(Escapable) { @Test func f() {} }":
         "Attribute 'Test' cannot be applied to a function within structure 'S' because its conformance to 'Escapable' has been suppressed",
+
+      // empty display name string literal
+      #"@Test("") func f() {}"#:
+        "Attribute 'Test' specifies an empty display name for this function",
+      ##"@Test(#""#) func f() {}"##:
+        "Attribute 'Test' specifies an empty display name for this function",
+      #"@Suite("") struct S {}"#:
+        "Attribute 'Suite' specifies an empty display name for this structure",
     ]
   )
   func apiMisuseErrors(input: String, expectedMessage: String) throws {
@@ -304,14 +312,6 @@ struct TestDeclarationMacroTests {
       // .serialized on a non-parameterized test function
       "@Test(.serialized) func f() {}":
         "Trait '.serialized' has no effect when used with a non-parameterized test function",
-
-      // empty display name string literal
-      #"@Test("") func f() {}"#:
-        "Attribute 'Test' specifies an empty display name for this function",
-      ##"@Test(#""#) func f() {}"##:
-        "Attribute 'Test' specifies an empty display name for this function",
-      #"@Suite("") struct S {}"#:
-        "Attribute 'Suite' specifies an empty display name for this structure",
     ]
   )
   func apiMisuseWarnings(input: String, expectedMessage: String) throws {