Add unit tests for HTTP commands. (#8267)

# Description

Following the comment from @fdncred:
https://github.com/nushell/nushell/pull/8144#issuecomment-1442514338. I
added some unit tests for HTTP commands. The tests are not exhaustive,
but at least, this is a first good step IMO.

# User-Facing Changes

None.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-command/tests/commands/network/http/get.rs

@@ -0,0 +1,44 @@
+use mockito::Server;
+use nu_test_support::{nu, pipeline};
+use reqwest::StatusCode;
+
+#[test]
+fn http_get_is_success() {
+    let mut server = Server::new();
+
+    let _mock = server.mock("GET", "/").with_body("foo").create();
+
+    let actual = nu!(pipeline(
+        format!(
+            r#"
+        http get {url}
+        "#,
+            url = server.url()
+        )
+        .as_str()
+    ));
+
+    assert_eq!(actual.out, "foo")
+}
+
+#[test]
+fn http_get_failed_due_to_server_error() {
+    let mut server = Server::new();
+
+    let _mock = server
+        .mock("GET", "/")
+        .with_status(StatusCode::BAD_REQUEST.as_u16() as usize)
+        .create();
+
+    let actual = nu!(pipeline(
+        format!(
+            r#"
+        http get {url}
+        "#,
+            url = server.url()
+        )
+        .as_str()
+    ));
+
+    assert!(actual.err.contains("Bad request (400)"))
+}