"RSpec doesn't work!" The cause was spring, so I investigated it.

I installed RSpec in an application, and when I ran the test code, I got an error. No matter how many times I review it, there should be no problem with the settings and description, but why doesn't it work? ..

** The cause was a gem called "spring". ** ** I entered the following command in the app directory and ran the test code again and it worked fine. Was good.

mac@ myApp % spring stop
Spring stopped.← OK if this notation appears

By the way, don't worry, this spring will restart automatically when you enter the rails command.

Who is this spring?

Simply put, it's like a rails cache. It is installed by default in Gemfile when rails new.

In this case, the cache before the introduction of RSpec happens to remain, If you execute the test code in that state, it seems that you get an error saying "RSpec cannot be used".

By the way, to check the status of spring, you can check it like this.

mac@ myApp % spring status
Spring is running:

97404 spring server | myApp | started 10 secs ago   
97405 spring app    | myApp | started 10 secs ago | development mode   

If you enter in the order of spring stop → rails c → ʻexit→spring status`, it will look like this.

mac@ myApp % spring stop
Spring stopped.　

mac@ myApp % rails c
Running via Spring preloader in process 97418
Loading development environment (Rails 6.0.3.2)
irb(main):001:0> exit

mac@ myApp % spring status
Spring is running:

97404 spring server | myApp | started 10 secs ago   
97405 spring app    | myApp | started 10 secs ago | development mode

mac@ ps aux | grep spring
mac        97139 101.0  0.5  4370124  43216   ??  Rs    2:24AM   0:00.73 spring app    | myApp3 | started 0 secs ago | development mode      
mac        97106   0.2  0.3  4352516  24104 s002  S     2:24AM   0:00.42 spring server | myApp3 | started 39 secs ago   
mac        96929   0.0  1.2  4462288 100216   ??  Ss    2:20AM   0:03.23 spring app    | myApp2 | started 4 mins ago | development mode      
mac        77394   0.0  0.1  4352516   8816   ??  S     05PM     0:01.03 spring server | myApp2 | started 56 hours ago   
mac         4764   0.0  0.0  4486444    472   ??  Ss    5 720    1:18.61 spring app    | myApp1 | started 439 hours ago | development mode      
mac         4760   0.0  0.0  4351492    432   ??  S     5 720    0:01.58 spring server | myApp1 | started 439 hours ago   
mac        97142   0.0  0.0  4276476    696 s002  S+    2:24AM   0:00.00 grep spring

I wondered if I could stop it with the kill command, but I couldn't stop it because it was restored immediately. After all it seems better to move to the corresponding directory and obediently spring stop.