tests: subscription encoding

Tests/NostrKitTests/Tests.swift

@@ -2,7 +2,38 @@ import XCTest
 @testable import NostrKit
 
 final class Tests: XCTestCase {
-    func test() throws {
-        // todo
+    func testMessageEncodingSubscription() throws {
+        let now = Timestamp(date: Date())
+        let then = Timestamp(date: Date.distantFuture)
+
+        let subscription = Subscription(filters: [
+            .init(
+                ids: ["foo"],
+                authors: ["bar"],
+                eventKinds: [.textNote],
+                tags: ["e": ["foo", "bar"], "p": ["bar", "foo"]],
+                since: now,
+                until: then,
+                limit: 10)
+        ])
+
+        let message = ClientMessage.subscribe(subscription)
+        let encoded = try JSONEncoder().encode(message)
+
+        let decodedMessage = try JSONSerialization.jsonObject(with: encoded) as! [Any]
+
+        XCTAssertEqual(decodedMessage[0] as! String, "REQ")
+        XCTAssertNotNil(decodedMessage[1] as? String)
+
+        let decodedFilter = decodedMessage[2] as! [String: Any]
+
+        XCTAssertEqual(decodedFilter["ids"] as! [String], ["foo"])
+        XCTAssertEqual(decodedFilter["authors"] as! [String], ["bar"])
+        XCTAssertEqual(decodedFilter["kinds"] as! [Int], [1])
+        XCTAssertEqual(decodedFilter["#e"] as! [String], ["foo", "bar"])
+        XCTAssertEqual(decodedFilter["#p"] as! [String], ["bar", "foo"])
+        XCTAssertEqual(decodedFilter["since"] as! Int, now.timestamp)
+        XCTAssertEqual(decodedFilter["until"] as! Int, then.timestamp)
+        XCTAssertEqual(decodedFilter["limit"] as! Int, 10)
     }
 }