Add do tests

Signed-off-by: Joel Longtine <joel@dagger.io>

tests/plan/do/dynamic_tasks.cue

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"dagger.io/dagger"
+
+	"universe.dagger.io/alpine"
+	"universe.dagger.io/bash"
+)
+
+dagger.#Plan & {
+	outputs: files: andrea: {
+		dest:     "./andrea_do"
+		contents: actions.test.b.y.export.files["/output.txt"]
+	}
+
+	actions: {
+		image: alpine.#Build & {
+			packages: bash: {}
+		}
+
+		test: {
+			a: bash.#Run & {
+				input: image.output
+				script: contents: "echo -n 'from andrea with love' > /output.txt"
+				export: files: "/output.txt": string
+			}
+			b: {
+				x: bash.#Run & {
+					input: image.output
+					script: contents: "echo -n testing > /output.txt"
+					export: files: "/output.txt": string
+				}
+				// This fails. Building the Actions lookup table breaks
+				if x.export.files["/output.txt"] == "testing" {
+					y: bash.#Run & {
+						input: a.output
+						script: contents: "echo -n hello from y"
+						export: files: "/output.txt": string
+					}
+				}
+			}
+		}
+
+		// notMe: bash.#Run & {
+		//  input: image.output
+		//  script: contents: "false"
+		// }
+	}
+}