Add test and don't throw errors (#37)

executable/Install.re

@@ -93,6 +93,15 @@ let run = (~version) =>
       </Pastel>,
     )
     |> Lwt.return
+  | Versions.Already_installed(version) =>
+    Console.log(
+      <Pastel>
+        "Version "
+        <Pastel color=Pastel.Cyan> version </Pastel>
+        " is already installed."
+      </Pastel>,
+    )
+    |> Lwt.return
   | Versions.Version_not_found(version) =>
     Console.log(
       <Pastel>

feature_tests/existing_installation/run.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+eval `fnm env`
+
+fnm install v8.11.3
+fnm install v8.11.3 | grep "already installed"
+
+if [ "$?" != "0" ]; then
+  echo "The second installation should say it is already installed"
+  exit 1
+fi