yarn: cleanup tests

Signed-off-by: Solomon Hykes <solomon@dagger.io>

pkg/universe.dagger.io/yarn/test/test.cue

@@ -0,0 +1,61 @@
+package yarn
+
+import (
+	"dagger.io/dagger"
+	"dagger.io/dagger/engine"
+
+	"universe.dagger.io/yarn"
+)
+
+dagger.#Plan & {
+	inputs: directories: {
+		testdata: path:  "./data/foo"
+		testdata2: path: "./data/bar"
+	}
+
+	actions: tests: {
+
+		// Run yarn.#Build
+		simple: {
+			build: yarn.#Build & {
+				source: inputs.directories.testdata.contents
+			}
+
+			verify: #AssertFile & {
+				input:    build.output
+				path:     "test"
+				contents: "output\n"
+			}
+		}
+
+		// Run yarn.#Build with a custom name
+		customName: {
+			build: yarn.#Build & {
+				name:   "My Build"
+				source: inputs.directories.testdata.contents
+			}
+			verify: #AssertFile & {
+				input:    build.output
+				path:     "test"
+				contents: "output\n"
+			}
+		}
+	}
+}
+
+// Make an assertion on the contents of a file
+#AssertFile: {
+	input:    dagger.#FS
+	path:     string
+	contents: string
+
+	_read: engine.#ReadFile & {
+		"input": input
+		"path":  path
+	}
+
+	actual: _read.contents
+
+	// Assertion
+	contents: actual
+}