Fix test_issue_588

Tests/AppTests/GitlabBuilderTests.swift

@@ -99,25 +99,23 @@ class GitlabBuilderTests: AppTestCase {
     }
 
     func test_issue_588() async throws {
+        let called = QueueIsolated(false)
         try await withDependencies {
             $0.environment.awsDocsBucket = { "docs-bucket" }
             $0.environment.builderToken = { "builder token" }
             $0.environment.buildTimeout = { 10 }
             $0.environment.gitlabPipelineToken = { "pipeline token" }
             $0.environment.siteURL = { "http://example.com" }
-        } operation: {
-            var called = false
-            let client = MockClient { req, res in
-                called = true
-                try? res.content.encode(
-                    Gitlab.Builder.Response.init(webUrl: "http://web_url")
-                )
+            $0.httpClient.post = { @Sendable _, _, body in
+                called.setTrue()
+                let body = try XCTUnwrap(body)
                 // validate
-                let swiftVersion = (try? req.query.decode(Gitlab.Builder.PostDTO.self))
+                let swiftVersion = (try? JSONDecoder().decode(Gitlab.Builder.PostDTO.self, from: body))
                     .flatMap { $0.variables["SWIFT_VERSION"] }
                 XCTAssertEqual(swiftVersion, "6.0")
+                return try .created(jsonEncode: Gitlab.Builder.Response.init(webUrl: "http://web_url"))
             }
-
+        } operation: {
             // MUT
             _ = try await Gitlab.Builder.triggerBuild(buildId: .id0,
                                                       cloneURL: "https://github.com/daveverwer/LeftPad.git",
@@ -126,7 +124,7 @@ class GitlabBuilderTests: AppTestCase {
                                                       reference: .tag(.init(1, 2, 3)),
                                                       swiftVersion: .v6_0,
                                                       versionID: .id1)
-            XCTAssertTrue(called)
+            XCTAssertTrue(called.value)
         }
     }