Cli tool tests (#977)

* add tests and fix some minor things

* implement output writer and some tests

* formatting

* adjust tests and formatting

* clippy fix

* cargo fmt

* revert change in substrate runner

* clippy suggestions

* mode make_type to test mod

cli/src/commands/metadata.rs

@@ -7,7 +7,7 @@ use clap::Parser as ClapParser;
 use codec::{Decode, Encode};
 use color_eyre::eyre::{self, bail};
 use frame_metadata::{v15::RuntimeMetadataV15, RuntimeMetadata, RuntimeMetadataPrefixed};
-use std::io::{self, Write};
+use std::io::Write;
 use subxt_metadata::Metadata;
 
 /// Download metadata from a substrate node, for use with `subxt` codegen.
@@ -34,7 +34,7 @@ pub struct Opts {
     runtime_apis: Option<Vec<String>>,
 }
 
-pub async fn run(opts: Opts) -> color_eyre::Result<()> {
+pub async fn run(opts: Opts, output: &mut impl Write) -> color_eyre::Result<()> {
     let bytes = opts.file_or_url.fetch().await?;
     let mut metadata = RuntimeMetadataPrefixed::decode(&mut &bytes[..])?;
 
@@ -72,17 +72,18 @@ pub async fn run(opts: Opts) -> color_eyre::Result<()> {
     match opts.format.as_str() {
         "json" => {
             let json = serde_json::to_string_pretty(&metadata)?;
-            println!("{json}");
+            write!(output, "{json}")?;
             Ok(())
         }
         "hex" => {
             let hex_data = format!("0x{:?}", hex::encode(metadata.encode()));
-            println!("{hex_data}");
+            write!(output, "{hex_data}")?;
             Ok(())
         }
         "bytes" => {
             let bytes = metadata.encode();
-            Ok(io::stdout().write_all(&bytes)?)
+            output.write_all(&bytes)?;
+            Ok(())
         }
         _ => Err(eyre::eyre!(
             "Unsupported format `{}`, expected `json`, `hex` or `bytes`",