Test are using relative paths:

- ensure AnyCPU path depth matches x86/x64

build.cake

@@ -740,7 +740,7 @@ Task ("tests")
         DotNetBuild ("./tests/SkiaSharp.Desktop.Tests/SkiaSharp.Desktop.Tests.sln", c => { 
             c.Configuration = "Release"; 
         });
-        RunTests("./tests/SkiaSharp.Desktop.Tests/bin/Release/SkiaSharp.Desktop.Tests.dll");
+        RunTests("./tests/SkiaSharp.Desktop.Tests/bin/AnyCPU/Release/SkiaSharp.Desktop.Tests.dll");
     }
 });
 

tests/SkiaSharp.Desktop.Tests/SkiaSharp.Desktop.Tests.csproj

@@ -16,7 +16,7 @@
     <DebugSymbols>true</DebugSymbols>
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
-    <OutputPath>bin\Debug\</OutputPath>
+    <OutputPath>bin\AnyCPU\Debug\</OutputPath>
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
@@ -24,7 +24,7 @@
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
     <Optimize>true</Optimize>
-    <OutputPath>bin\Release\</OutputPath>
+    <OutputPath>bin\AnyCPU\Release\</OutputPath>
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>