Add simple test environment for core features

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

tests/core.bats

@@ -0,0 +1,30 @@
+# Test core Dagger features & types
+
+setup() {
+    load 'helpers'
+
+    common_setup
+
+    # Use native Dagger environment here
+    unset DAGGER_WORKSPACE
+}
+
+@test "core: inputs" {
+   # List available inputs
+   run dagger -e test-core input list
+   assert_success
+   assert_output --partial 'name'
+   assert_output --partial 'dir'
+
+   # Set text input
+   dagger -e test-core input text name Bob
+   run dagger -e test-core up
+   assert_success
+   assert_output --partial 'Hello, Bob!'
+
+   # Unset text input
+   dagger -e test-core input unset name
+   run dagger -e test-core up
+   assert_success
+   assert_output --partial 'Hello, world!'
+}