Add tests on docker.#Build definition

- Simple build test
- Multi step to build a go binary

Signed-off-by: Vasek - Tom C <tom.chauveau@epitech.eu>

pkg/universe.dagger.io/docker/test/build-multi-steps.cue

@@ -0,0 +1,49 @@
+package test
+
+import (
+	"dagger.io/dagger"
+	"dagger.io/dagger/engine"
+	"universe.dagger.io/docker"
+)
+
+// This test verify that we can correctly build an image
+// using docker.#Build with multiple steps executed during
+// the building process
+dagger.#Plan & {
+	inputs: directories: testdata: path: "./testdata"
+
+	actions: {
+		image: docker.#Build & {
+			steps: [
+				docker.#Pull & {
+					source: "golang:1.17-alpine"
+				},
+				docker.#Copy & {
+					contents: inputs.directories.testdata.contents
+					dest:     "/input"
+				},
+				docker.#Run & {
+					script: """
+							# FIXME remove that line when #1517 is merged
+							export PATH=/go/bin:/usr/local/go/bin:$PATH
+							go build -o hello ./main.go
+							mv hello /bin
+						"""
+					workdir: "/input"
+				},
+				docker.#Run & {
+					script: """
+							hello >> /test.txt
+						"""
+				},
+			]
+		}
+
+		verify: engine.#ReadFile & {
+			input: image.output.rootfs
+			path:  "/test.txt"
+		} & {
+			contents: "hello world"
+		}
+	}
+}