Implement updates to testing framework based on recent feedback

internal/command/testdata/test/only_modules/example/main.tf

@@ -0,0 +1,9 @@
+
+variable "input" {
+  type = string
+}
+
+resource "test_resource" "module_resource" {
+  id = "df6h8as9"
+  value = var.input
+}

internal/command/testdata/test/only_modules/main.tf

@@ -0,0 +1,9 @@
+
+variable "input" {
+  type = string
+}
+
+resource "test_resource" "resource" {
+  id = "598318e0"
+  value = var.input
+}

internal/command/testdata/test/only_modules/main.tftest.hcl

@@ -0,0 +1,23 @@
+# This is an example test file from a use case requested by a user. We only
+# refer to alternate modules and not the main configuration. This means we
+# shouldn't have to provide any data for the main configuration.
+
+run "first" {
+  module {
+    source = "./example"
+  }
+
+  variables {
+    input = "start"
+  }
+}
+
+run "second" {
+  module {
+    source = "./example"
+  }
+
+  variables {
+    input = "update"
+  }
+}