fix: Do not pre-pull scratch image (#1304)

Author: HofmeisterAn

src/Testcontainers/Clients/TestcontainersClient.cs

@@ -383,6 +383,12 @@ private async Task PullImageAsync(IImage image, CancellationToken ct = default)
 
       if (dockerRegistryServerAddress == null)
       {
+        // https://hub.docker.com/_/scratch.
+        if ("scratch".Equals(image.Repository, StringComparison.OrdinalIgnoreCase))
+        {
+          return;
+        }
+
         var info = await System.GetInfoAsync(ct)
           .ConfigureAwait(false);
 

tests/Testcontainers.Tests/Assets/.dockerignore

@@ -3,4 +3,5 @@ credHelpers
 credsStore
 healthWaitStrategy
 pullBaseImages
+scratch
 **/*.md

tests/Testcontainers.Tests/Assets/scratch/Dockerfile

@@ -0,0 +1,2 @@
+FROM scratch
+LABEL "maintainer"="[email protected]"

tests/Testcontainers.Tests/Unit/Images/ImageFromDockerfileTest.cs

@@ -100,11 +100,31 @@ public async Task ThrowsDockerfileDirectoryDoesNotExist()
       Assert.Equal($"Directory '{Path.GetFullPath(dockerfileDirectory)}' does not exist.", exception.Message);
     }
 
+    [Fact]
+    public async Task BuildsDockerScratchImage()
+    {
+      // Given
+      var imageFromDockerfileBuilder = new ImageFromDockerfileBuilder()
+        .WithDockerfileDirectory("Assets/scratch")
+        .Build();
+
+      // When
+      var exception = await Record.ExceptionAsync(() => imageFromDockerfileBuilder.CreateAsync())
+        .ConfigureAwait(true);
+
+      // Then
+      Assert.Null(exception);
+      Assert.NotNull(imageFromDockerfileBuilder.Repository);
+      Assert.NotNull(imageFromDockerfileBuilder.Tag);
+      Assert.NotNull(imageFromDockerfileBuilder.FullName);
+      Assert.Null(imageFromDockerfileBuilder.GetHostname());
+    }
+
     [Theory]
     [InlineData("Dockerfile")]
     [InlineData("./Dockerfile")]
     [InlineData(".\\Dockerfile")]
-    public async Task BuildsDockerImage(string dockerfile)
+    public async Task BuildsDockerAlpineImage(string dockerfile)
     {
       // Given
       IImage tag1 = new DockerImage(new DockerImage(string.Join("/", "localhost", "testcontainers", Guid.NewGuid().ToString("D"))));