Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/format_conversions/sqlite.rs

@@ -0,0 +1,36 @@
+#[cfg(feature = "sqlite")]
+use nu_test_support::{nu, pipeline};
+
+#[cfg(feature = "sqlite")]
+#[test]
+fn table_to_sqlite_and_back_into_table() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open sample.db
+            | to sqlite
+            | from sqlite
+            | get table_values
+            | nth 2
+            | get x
+        "#
+    ));
+
+    assert_eq!(actual.out, "hello");
+}
+
+#[cfg(feature = "sqlite")]
+#[test]
+fn table_to_sqlite_and_back_into_table_select_table() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open sample.db
+            | to sqlite
+            | from sqlite -t [strings]
+            | get table_names
+        "#
+    ));
+
+    assert_eq!(actual.out, "strings");
+}