Add test coverage for base64 data helper methods (#114)

Tests/MCPTests/Base64DataTests.swift

@@ -0,0 +1,142 @@
+import Foundation
+import Testing
+
+@testable import MCP
+
+@Suite("Base64 Data Tests")
+struct Base64DataTests {
+
+    @Test("Check valid data URLs")
+    func testIsDataURL() {
+        // Basic valid data URL
+        #expect(Data.isDataURL(string: "data:,A%20brief%20note"))
+
+        // Valid image data URL from RFC example
+        #expect(
+            Data.isDataURL(string: "data:image/gif;base64,R0lGODdhMAAwAPAAAAAAAP///ywAAAAAMAAw"))
+
+        // Valid data URL with charset parameter
+        #expect(Data.isDataURL(string: "data:text/plain;charset=iso-8859-7,%be%fg%be"))
+
+        // Valid custom application type from RFC example
+        #expect(
+            Data.isDataURL(
+                string: "data:application/vnd-xxx-query,select_vcount,fcol_from_fieldtable/local"))
+
+        // Valid with implicit mediatype (defaults to text/plain)
+        #expect(Data.isDataURL(string: "data:,hello%20world"))
+
+        // Valid with just charset parameter
+        #expect(Data.isDataURL(string: "data:;charset=utf-8,hello"))
+    }
+
+    @Test("Check invalid data URLs")
+    func testInvalidDataURLs() {
+        // Not a data URL
+        #expect(!Data.isDataURL(string: "https://example.com"))
+
+        // Missing comma separator
+        #expect(!Data.isDataURL(string: "data:text/plain"))
+
+        // Malformed scheme
+        #expect(!Data.isDataURL(string: "dat:,hello"))
+
+        // Empty string
+        #expect(!Data.isDataURL(string: ""))
+    }
+
+    @Test("Parse data URL with plain text")
+    func testParseDataURLPlainText() {
+        // Example from RFC 2397
+        let result = Data.parseDataURL("data:,A%20brief%20note")
+        #expect(result != nil)
+        if let (mimeType, data) = result {
+            #expect(mimeType == "text/plain")
+            #expect(String(data: data, encoding: .utf8) == "A brief note")
+        }
+    }
+
+    @Test("Parse data URL with charset")
+    func testParseDataURLWithCharset() {
+        // Modified example from RFC 2397 (using valid percent encoding)
+        let result = Data.parseDataURL(
+            "data:text/plain;charset=iso-8859-7,%CF%84%CE%B5%CF%83%CF%84")
+        #expect(result != nil)
+        if let (mimeType, _) = result {
+            #expect(mimeType == "text/plain;charset=iso-8859-7")
+        }
+    }
+
+    @Test("Parse data URL with base64 encoding")
+    func testParseDataURLBase64() {
+        // Simple base64 encoded "Hello"
+        let result = Data.parseDataURL("data:text/plain;base64,SGVsbG8=")
+        #expect(result != nil)
+        if let (mimeType, data) = result {
+            #expect(mimeType == "text/plain")
+            #expect(String(data: data, encoding: .utf8) == "Hello")
+        }
+    }
+
+    @Test("Parse data URL with implicit text/plain")
+    func testParseDataURLImplicitTextPlain() {
+        let result = Data.parseDataURL("data:,hello%20world")
+        #expect(result != nil)
+        if let (mimeType, data) = result {
+            #expect(mimeType == "text/plain")
+            #expect(String(data: data, encoding: .utf8) == "hello world")
+        }
+    }
+
+    @Test("Parse invalid data URLs")
+    func testParseInvalidDataURLs() {
+        // Not a data URL
+        #expect(Data.parseDataURL("https://example.com") == nil)
+
+        // Malformed base64
+        #expect(Data.parseDataURL("data:text/plain;base64,SGVsbG8=!") == nil)
+
+        // Empty base64 data (valid according to RFC 2397)
+        let result = Data.parseDataURL("data:text/plain;base64,")
+        #expect(result != nil)
+        if let (mimeType, data) = result {
+            #expect(mimeType == "text/plain")
+            #expect(data.isEmpty)
+        }
+    }
+
+    @Test("Test data URL encoding")
+    func testDataURLEncoding() {
+        let testData = "Hello, world!".data(using: .utf8)!
+
+        // Default mime type (text/plain)
+        let url1 = testData.dataURLEncoded()
+        #expect(url1.hasPrefix("data:text/plain;base64,"))
+        #expect(Data.isDataURL(string: url1))
+
+        // Custom mime type
+        let url2 = testData.dataURLEncoded(mimeType: "application/octet-stream")
+        #expect(url2.hasPrefix("data:application/octet-stream;base64,"))
+        #expect(Data.isDataURL(string: url2))
+
+        // Roundtrip test
+        if let (mimeType, data) = Data.parseDataURL(url2) {
+            #expect(mimeType == "application/octet-stream")
+            #expect(data == testData)
+        } else {
+            #expect(Bool(false), "Failed to parse encoded data URL")
+        }
+    }
+
+    @Test("Test complex example from RFC 2397")
+    func testComplexExample() {
+        // Partial example of image from RFC (shortened for test brevity)
+        let dataURL = "data:image/gif;base64,R0lGODdhMAAwAPAAAAAAAP///ywAAAAAMAAw"
+
+        let result = Data.parseDataURL(dataURL)
+        #expect(result != nil)
+        if let (mimeType, _) = result {
+            #expect(mimeType == "image/gif")
+        }
+    }
+}