Add unit tests for Citation

Author: andrewheard

FirebaseAI/Tests/Unit/Types/CitationTests.swift

@@ -0,0 +1,113 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import FirebaseAI
+import XCTest
+
+@available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
+final class CitationTests: XCTestCase {
+  let decoder = JSONDecoder()
+
+  // MARK: - Decoding Tests
+
+  func testDecodeCitation_minimalParameters() throws {
+    let expectedEndIndex = 150
+    let json = """
+    {
+      "endIndex" : \(expectedEndIndex)
+    }
+    """
+    let jsonData = try XCTUnwrap(json.data(using: .utf8))
+
+    let citation = try decoder.decode(Citation.self, from: jsonData)
+
+    XCTAssertEqual(citation.startIndex, 0, "Omitted startIndex should be decoded as 0.")
+    XCTAssertEqual(citation.endIndex, expectedEndIndex)
+    XCTAssertNil(citation.uri)
+    XCTAssertNil(citation.title)
+    XCTAssertNil(citation.license)
+    XCTAssertNil(citation.publicationDate)
+  }
+
+  func testDecodeCitation_allParameters() throws {
+    let expectedStartIndex = 100
+    let expectedEndIndex = 200
+    let expectedURI = "https://example.com/citation-1"
+    let expectedTitle = "Example Citation Title"
+    let expectedLicense = "mit"
+    let expectedYear = 2023
+    let expectedMonth = 10
+    let expectedDay = 26
+    let json = """
+    {
+      "startIndex" : \(expectedStartIndex),
+      "endIndex" : \(expectedEndIndex),
+      "uri" : "\(expectedURI)",
+      "title" : "\(expectedTitle)",
+      "license" : "\(expectedLicense)",
+      "publicationDate" : {
+        "year" : \(expectedYear),
+        "month" : \(expectedMonth),
+        "day" : \(expectedDay)
+      }
+    }
+    """
+    let jsonData = try XCTUnwrap(json.data(using: .utf8))
+
+    let citation = try decoder.decode(Citation.self, from: jsonData)
+
+    XCTAssertEqual(citation.startIndex, expectedStartIndex)
+    XCTAssertEqual(citation.endIndex, expectedEndIndex)
+    XCTAssertEqual(citation.uri, expectedURI)
+    XCTAssertEqual(citation.title, expectedTitle)
+    XCTAssertEqual(citation.license, expectedLicense)
+    let publicationDate = try XCTUnwrap(citation.publicationDate)
+    XCTAssertEqual(publicationDate.year, expectedYear)
+    XCTAssertEqual(publicationDate.month, expectedMonth)
+    XCTAssertEqual(publicationDate.day, expectedDay)
+  }
+
+  func testDecodeCitation_emptyStringsForOptionals_setsToNil() throws {
+    let expectedEndIndex = 300
+    let json = """
+    {
+      "endIndex" : \(expectedEndIndex),
+      "uri" : "",
+      "title" : "",
+      "license" : ""
+    }
+    """
+    let jsonData = try XCTUnwrap(json.data(using: .utf8))
+
+    let citation = try decoder.decode(Citation.self, from: jsonData)
+
+    XCTAssertEqual(citation.startIndex, 0, "Omitted startIndex should be decoded as 0.")
+    XCTAssertEqual(citation.endIndex, expectedEndIndex)
+    XCTAssertNil(citation.uri, "Empty URI string should be decoded as nil.")
+    XCTAssertNil(citation.title, "Empty title string should be decoded as nil.")
+    XCTAssertNil(citation.license, "Empty license string should be decoded as nil.")
+    XCTAssertNil(citation.publicationDate)
+  }
+
+  func testDecodeCitation_missingEndIndex_throws() throws {
+    let json = """
+    {
+      "startIndex" : 10
+    }
+    """
+    let jsonData = try XCTUnwrap(json.data(using: .utf8))
+
+    XCTAssertThrowsError(try decoder.decode(Citation.self, from: jsonData))
+  }
+}