Add isFailure to Issue (#1078)

Add `isFailure` var to `Issue`

### Motivation:

This adds a variable to `Issue` in order to inspect if an issue
isFailing. This will be nice when inspecting an issue after it is
recorded.

### Modifications:

- Add `isFailure` variable
- Update existing code to use `isFailure` 

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: suzannaratcliff

Sources/Testing/ABI/EntryPoints/EntryPoint.swift

@@ -42,7 +42,7 @@ func entryPoint(passing args: __CommandLineArguments_v0?, eventHandler: Event.Ha
 
     // Set up the event handler.
     configuration.eventHandler = { [oldEventHandler = configuration.eventHandler] event, context in
-      if case let .issueRecorded(issue) = event.kind, !issue.isKnown, issue.severity >= .error {
+      if case let .issueRecorded(issue) = event.kind, issue.isFailure {
         exitCode.withLock { exitCode in
           exitCode = EXIT_FAILURE
         }

Sources/Testing/Issues/Issue.swift

@@ -103,6 +103,21 @@ public struct Issue: Sendable {
   /// The severity of this issue.
   @_spi(Experimental)
   public var severity: Severity
+  
+  /// Whether or not this issue should cause the test it's associated with to be
+  /// considered a failure.
+  ///
+  /// The value of this property is `true` for issues which have a severity level of
+  /// ``Issue/Severity/error`` or greater and are not known issues via
+  /// ``withKnownIssue(_:isIntermittent:sourceLocation:_:when:matching:)``.
+  /// Otherwise, the value of this property is `false.`
+  ///
+  /// Use this property to determine if an issue should be considered a failure, instead of
+  /// directly comparing the value of the ``severity`` property.
+  @_spi(Experimental)
+  public var isFailure: Bool {
+    return !self.isKnown && self.severity >= .error
+  }
 
   /// Any comments provided by the developer and associated with this issue.
   ///

Tests/TestingTests/IssueTests.swift

@@ -1011,6 +1011,7 @@ final class IssueTests: XCTestCase {
       }
       XCTAssertFalse(issue.isKnown)
       XCTAssertEqual(issue.severity, .error)
+      XCTAssertTrue(issue.isFailure)
       guard case .unconditional = issue.kind else {
         XCTFail("Unexpected issue kind \(issue.kind)")
         return
@@ -1031,6 +1032,7 @@ final class IssueTests: XCTestCase {
       }
       XCTAssertFalse(issue.isKnown)
       XCTAssertEqual(issue.severity, .warning)
+      XCTAssertFalse(issue.isFailure)
       guard case .unconditional = issue.kind else {
         XCTFail("Unexpected issue kind \(issue.kind)")
         return

Tests/TestingTests/KnownIssueTests.swift

@@ -10,7 +10,7 @@
 
 #if canImport(XCTest)
 import XCTest
-@testable @_spi(ForToolsIntegrationOnly) import Testing
+@testable @_spi(Experimental) @_spi(ForToolsIntegrationOnly) import Testing
 
 final class KnownIssueTests: XCTestCase {
   func testIssueIsKnownPropertyIsSetCorrectly() async {
@@ -26,6 +26,7 @@ final class KnownIssueTests: XCTestCase {
       issueRecorded.fulfill()
 
       XCTAssertTrue(issue.isKnown)
+      XCTAssertFalse(issue.isFailure)
     }
 
     await Test {