Add slot-time CLI argument

beacon_node/src/config.rs

@@ -74,7 +74,7 @@ fn process_testnet_subcommand(
 
     if let Some(path_string) = cli_args.value_of("eth2-config") {
         if is_bootstrap {
-            return Err("Cannot supply --eth2-config when using bootsrap".to_string());
+            return Err("Cannot supply --eth2-config when using bootstrap".to_string());
         }
 
         let path = path_string
@@ -85,6 +85,18 @@ fn process_testnet_subcommand(
         builder.update_spec_from_subcommand(&cli_args)?;
     }
 
+    if let Some(slot_time) = cli_args.value_of("slot-time") {
+        if is_bootstrap {
+            return Err("Cannot supply --slot-time flag whilst using bootstrap.".into());
+        }
+
+        let slot_time = slot_time
+            .parse::<u64>()
+            .map_err(|e| format!("Unable to parse slot-time: {:?}", e))?;
+
+        builder.set_slot_time(slot_time);
+    }
+
     if let Some(path_string) = cli_args.value_of("client-config") {
         let path = path_string
             .parse::<PathBuf>()
@@ -307,6 +319,10 @@ impl<'a> ConfigBuilder<'a> {
         self.eth2_config = eth2_config;
     }
 
+    fn set_slot_time(&mut self, milliseconds_per_slot: u64) {
+        self.eth2_config.spec.milliseconds_per_slot = milliseconds_per_slot;
+    }
+
     /// Reads the subcommand and tries to update `self.eth2_config` based up on the `--spec` flag.
     ///
     /// Returns an error if the `--spec` flag is not present in the given `cli_args`.

beacon_node/src/main.rs

@@ -241,6 +241,13 @@ fn main() {
                            backup directory.")
                     .conflicts_with("random-datadir")
             )
+            .arg(
+                Arg::with_name("slot-time")
+                    .long("slot-time")
+                    .short("t")
+                    .value_name("MILLISECONDS")
+                    .help("Defines the slot time when creating a new testnet.")
+            )
             /*
              * `boostrap`
              *