Implemented the TemplateService service in the library target.

Test/Sources/Helpers/Spies/FileServiceSpy.swift

@@ -1,7 +1,6 @@
+import ColibriLibrary
 import Foundation
 
-@testable import ColibriLibrary
-
 final class FileServiceSpy {
     
     // MARK: Properties

Test/Sources/Helpers/Spies/TemplateServiceSpy.swift

@@ -0,0 +1,38 @@
+import ColibriLibrary
+
+final class TemplateServiceSpy {
+    
+    // MARK: Properties
+    
+    private(set) var actions: [Action] = []
+    
+}
+
+// MARK: - TemplateServicing
+
+extension TemplateServiceSpy: TemplateServicing {
+    
+    // MARK: Functions
+    
+    @discardableResult
+    func render(_ object: Any, on template: String) async throws(TemplateServiceError) -> String {
+        actions.append(.rendered(object, template))
+        
+        return .content
+    }
+    
+}
+
+// MARK: - Actions
+
+extension TemplateServiceSpy {
+    enum Action {
+        case rendered(_ object: Any, _ template: String)
+    }
+}
+
+// MARK: - String+Constants
+
+private extension String {
+    static let content = ""
+}