Improve test coverage

Package.swift

@@ -41,6 +41,8 @@ let package = Package(
                 .copy("Resources/alien.jpg"),
                 .copy("Resources/loading.lottie"),
                 .copy("Resources/ArialBlack.ttf"),
+                .copy("Resources/unknown"),
+                .copy("Resources/unsupported.extension"),
             ]
         ),
     ]

Sources/SnappThemingDesignTokensSupport/Convertor/DesignTokensConverter.swift

@@ -30,12 +30,14 @@ public struct DesignTokensConverter: Sendable {
         ///   - token: The `Token` that could not be processed.
         ///   - forKey: The key associated with the unsupported token.
         case unsupportedToken(Token, forKey: String)
+        case malformedDynamicColorsGroup(TokenGroup, forKey: String)
 
         /// A localized description of the error.
         public var errorDescription: String? {
             switch self {
             case .invalidRootToken: "Invalid root token. Must be a group."
             case let .unsupportedToken(_, key): "Unsupported token value type with key: \(key)."
+            case let .malformedDynamicColorsGroup(_, key): "Malformed dynamic colors group for key: \(key)."
             }
         }
     }
@@ -146,7 +148,7 @@ public struct DesignTokensConverter: Sendable {
             )
             try extractor.extract(value, for: key, into: &caches)
         case .group(let group):
-            try await extract(group, for: key, into: &caches)
+            try await extractDynamicColorsGroup(group, for: key, into: &caches)
         case .alias, .array, .unknown:
             throw Error.unsupportedToken(token, forKey: key)
         }
@@ -161,16 +163,20 @@ public struct DesignTokensConverter: Sendable {
     ///   - key: The key associated with the token group.
     ///   - caches: The `SnappThemingDeclarationCaches` to store the dynamic color.
     /// - Throws: `DesignTokensConverter.Error` if color conversion fails.
-    private func extract(
+    private func extractDynamicColorsGroup(
         _ group: TokenGroup,
         for key: String,
         into caches: inout SnappThemingDeclarationCaches
     ) async throws {
         guard
-            case .value(.color(let lightColorToken)) = group[configuration.dynamicColorKeys.light],
-            case .value(.color(let darkColorToken)) = group[configuration.dynamicColorKeys.dark]
+            case .value(.color(let lightColorToken)) = group[
+                configuration.dynamicColorKeys.light
+            ],
+            case .value(.color(let darkColorToken)) = group[
+                configuration.dynamicColorKeys.dark
+            ]
         else {
-            return
+            throw Error.malformedDynamicColorsGroup(group, forKey: key)
         }
 
         let lightColorHEX = try lightColorToken.hex(

Sources/SnappThemingDesignTokensSupport/Convertor/Extractor/DesignTokensFileValueExtractor.swift

@@ -9,11 +9,12 @@ import SnappDesignTokens
 import SnappTheming
 import UniformTypeIdentifiers
 
-extension DesignTokensTokenValueExtractor {
-    private enum ExtractionError: Error {
-        case invalidData
-    }
+enum DesignTokensFileValueExtractorError: Error, Equatable {
+    case unknownFileType(URL)
+    case unsupportedFileType(URL, UTType)
+}
 
+extension DesignTokensTokenValueExtractor {
     static var file: Self {
         .init {
             (
@@ -26,18 +27,14 @@ extension DesignTokensTokenValueExtractor {
                 options: .endLineWithLineFeed
             )
 
-            guard
-                let base64EncodedData = Data(base64Encoded: base64EncodedString)
-            else {
-                throw ExtractionError.invalidData
-            }
-
             guard
                 let contentType = UTType(
                     filenameExtension: fileValue.url.pathExtension
                 )
             else {
-                return
+                throw DesignTokensFileValueExtractorError.unknownFileType(
+                    fileValue.url
+                )
             }
 
             switch (
@@ -67,7 +64,7 @@ extension DesignTokensTokenValueExtractor {
                         source: SnappThemingDataURI(
                             type: contentType,
                             encoding: .base64,
-                            data: base64EncodedData
+                            data: data
                         )
                     )
                 )
@@ -76,11 +73,14 @@ extension DesignTokensTokenValueExtractor {
                 (_, _, .lotPathExtension):
                 caches.animationCache[key] = .value(
                     SnappThemingAnimationRepresentation(
-                        animation: .lottie(base64EncodedData)
+                        animation: .lottie(data)
                     )
                 )
             case (_, _, _):
-                break
+                throw DesignTokensFileValueExtractorError.unsupportedFileType(
+                    fileValue.url,
+                    contentType
+                )
             }
         }
     }

Sources/SnappThemingDesignTokensSupport/Convertor/Extractor/DesignTokensFontFamilyValueExtractor.swift

@@ -8,11 +8,11 @@ import Foundation
 import SnappDesignTokens
 import SnappTheming
 
-extension DesignTokensTokenValueExtractor {
-    private enum DesignTokensFontFamilyExtractionError: Error {
-        case fontsEmpty
-    }
+enum DesignTokensFontFamilyValueExtractionError: Error {
+    case fontsEmpty
+}
 
+extension DesignTokensTokenValueExtractor {
     static var fontFamily: Self {
         .init(\.fontsCache) { (value: FontFamilyValue) in
             /// As a [translation tool](https://tr.designtokens.org/format/#translation-tool) we
@@ -21,7 +21,7 @@ extension DesignTokensTokenValueExtractor {
             /// we will just try to use the primary font and ignore fallbacks.
             /// OS will just provided system font as fallback if required font is not available.
             guard let fontName = value.names.first else {
-                throw DesignTokensFontFamilyExtractionError.fontsEmpty
+                throw DesignTokensFontFamilyValueExtractionError.fontsEmpty
             }
             return SnappThemingFontInformation(postScriptName: fontName, source: nil)
         }

Sources/SnappThemingDesignTokensSupport/Convertor/Extractor/DesignTokensGradientValueExtractor.swift

@@ -8,19 +8,19 @@ import Foundation
 import SnappDesignTokens
 import SnappTheming
 
-extension DesignTokensTokenValueExtractor {
-    private enum GradientExtractionError: Error {
-        case unresolvedReferences
-    }
+enum DesignTokensGradientValueExtractionError: Error {
+    case unresolvedReferences
+}
 
+extension DesignTokensTokenValueExtractor {
     static func gradient(using format: ColorHexFormat) -> Self {
         .init(\.gradientsCache) { (value: GradientValue) in
             let colorsWithPositions = try value.map { gradientColorValue in
                 guard
                     case .value(let color) = gradientColorValue.color,
                     case .value(let position) = gradientColorValue.position
                 else {
-                    throw GradientExtractionError.unresolvedReferences
+                    throw DesignTokensGradientValueExtractionError.unresolvedReferences
                 }
                 return (
                     color,

Sources/SnappThemingDesignTokensSupport/Convertor/Extractor/DesignTokensTypographyValueExtractor.swift

@@ -8,14 +8,14 @@ import Foundation
 import SnappDesignTokens
 import SnappTheming
 
-extension DesignTokensTokenValueExtractor {
-    private enum TypographyExtractionError: Error {
-        case unresolvedReferences
-        case unresolvedExpressions
-        case invalidFontSizeUnit
-        case fontsEmpty
-    }
+enum DesignTokensTypographyValueExtractorError: Error, Equatable, Sendable {
+    case unresolvedReferences
+    case unresolvedExpressions
+    case invalidFontSizeUnit
+    case fontsEmpty
+}
 
+extension DesignTokensTokenValueExtractor {
     static func typography(
         fontWeightMapping: FontWeightMapping? = nil
     ) -> Self {
@@ -25,19 +25,22 @@ extension DesignTokensTokenValueExtractor {
                 case .value(let fontWeight) = value.fontWeight,
                 case .value(let fontSizeValue) = value.fontSize
             else {
-                throw TypographyExtractionError.unresolvedReferences
+                throw DesignTokensTypographyValueExtractorError
+                    .unresolvedReferences
             }
 
             guard let fontFamilyName = fontFamilyValue.names.first else {
-                throw TypographyExtractionError.fontsEmpty
+                throw DesignTokensTypographyValueExtractorError.fontsEmpty
             }
 
             guard case .constant(let fontSize) = fontSizeValue else {
-                throw TypographyExtractionError.unresolvedExpressions
+                throw DesignTokensTypographyValueExtractorError
+                    .unresolvedExpressions
             }
 
             guard fontSize.unit == .px else {
-                throw TypographyExtractionError.invalidFontSizeUnit
+                throw DesignTokensTypographyValueExtractorError
+                    .invalidFontSizeUnit
             }
 
             var fontName = fontFamilyName

Sources/SnappThemingDesignTokensSupport/Extensions/SnappThemingParser+DesignTokens.swift

@@ -37,9 +37,8 @@ extension SnappThemingParser {
         tokenProcessor processor: TokenProcessor = .defaultDesignTokensConversionProcessor(),
         designTokensConverterConfiguration configuration: DesignTokensConverter.Configuration = .default
     ) async throws -> SnappThemingDeclaration {
-        guard let data = input.data(using: .utf8) else {
-            throw SnappThemingParserError.invalidData
-        }
+        // It is safe to force unwrap since Strings in Swift use Unicode internally.
+        let data = input.data(using: .utf8)!
 
         let decoder = JSONDecoder()
         let token: Token

Tests/SnappThemingDesignTokensSupportTests/DesignTokensTokenValueExtractorTests.swift

@@ -0,0 +1,23 @@
+//
+//  DesignTokensTokenValueExtractorTests.swift
+//  SnappThemingDesignTokensSupport
+//
+//  Created by Volodymyr Voiko on 18.12.2025.
+//
+
+import Testing
+import SnappDesignTokens
+
+@testable import SnappThemingDesignTokensSupport
+
+struct DesignTokensTokenValueExtractorTests {
+    @Test
+    func testTypeMistmatchErrorHandling() async throws {
+        var caches = SnappThemingDeclarationCaches()
+        let extractor = DesignTokensTokenValueExtractor.color(using: .argb)
+        let tokenValue = TokenValue.number(0.5)
+        #expect(throws: DesignTokensTokenValueExtractorError.typeMistamatch) {
+            try extractor.extract(tokenValue, for: "key", into: &caches)
+        }
+    }
+}

Tests/SnappThemingDesignTokensSupportTests/Resources/unknown

@@ -0,0 +1 @@
+