Add a failing test for extracting the resolving issue from a pull request body

Author: AvdLee

Sources/ChangelogProducerCore/StringExtensions.swift

@@ -14,4 +14,9 @@ extension String {
     func pullRequestIDs() -> [Int] {
         return []
     }
+
+    /// Extracts the resolved issue from a Pull Request body.
+    func resolvingIssue() -> Int? {
+        return nil
+    }
 }

Tests/ChangelogProducerTests/ChangelogProducerTests.swift

@@ -4,7 +4,7 @@ import XCTest
 final class ChangelogProducerTests: XCTestCase {
 
     /// It should extract pull request IDs from squash merges.
-    func testPullRequestIDsFromSquashCommits() throws {
+    func testPullRequestIDsFromSquashCommits() {
         let gitLogOutput = """
             * Fix bucket deeplinking after adding content (#5130) via Antoine van der Lee
             * Fix CI for Coyote #trivial (#5114) via Antoine van der Lee
@@ -14,16 +14,49 @@ final class ChangelogProducerTests: XCTestCase {
     }
 
     /// It should extract pull request from merge commits.
-    func testPullRequestIDsFromMergeCommits() throws {
-            let gitLogOutput = """
-                * Merge pull request #65 from BalestraPatrick/profiles-devices-endpoints via Antoine van der Lee
-                * Merge pull request #62 from hexagons/issue/42 via Antoine van der Lee
-                """
-            XCTAssertEqual(gitLogOutput.pullRequestIDs(), [62, 65])
+    func testPullRequestIDsFromMergeCommits() {
+        let gitLogOutput = """
+            * Merge pull request #65 from BalestraPatrick/profiles-devices-endpoints via Antoine van der Lee
+            * Merge pull request #62 from hexagons/issue/42 via Antoine van der Lee
+            """
+        XCTAssertEqual(gitLogOutput.pullRequestIDs(), [62, 65])
+    }
+
+    /// It should extract the fixed issue from the Pull Request body.
+    func testResolvingReferencedIssue() {
+        // See this code as an example: https://github.com/fastlane/issue-bot/blob/457348717d99e5ffde34ca1619e7253ed51ec172/bot.rb#L456
+
+        let issueClosingKeywords = [
+            "close",
+            "Closes",
+            "closed",
+            "fix",
+            "fixes",
+            "Fixed",
+            "resolve",
+            "Resolves",
+            "resolved"
+        ]
+
+        issueClosingKeywords.forEach { (closingKeyword) in
+            let description = examplePullRequestDescriptionUsing(closingKeyword: closingKeyword)
+            XCTAssertEqual(description.resolvingIssue(), 4343)
         }
+    }
 
     static var allTests = [
         ("testPullRequestIDsFromSquashCommits", testPullRequestIDsFromSquashCommits),
         ("testPullRequestIDsFromMergeCommits", testPullRequestIDsFromMergeCommits)
     ]
 }
+
+extension ChangelogProducerTests {
+    func examplePullRequestDescriptionUsing(closingKeyword: String) -> String {
+        return """
+            This PR does a lot of awesome stuff.
+
+            \(closingKeyword) #4343
+            """
+
+    }
+}