How to ensure that Spyder runs within a conda environment?

Question

I created a conda environment called testenv in Windows 10 that contains Python 3.6 and Spyder. I also installed Selenium using the method described in this answer. I checked that these packages are installed with

conda list -n testenv

To run Spyder in that environment I followed the instructions in this answer and its related comments. So I activated the environment with

activate testenv

which modified the prompt to indicate that testenv is active. Then I typed

spyder

to launch Spyder. (When Spyder opens, my command window automatically closes, and if I open another one without closing Spyder, and I issue the command conda info -e, the output indicates that testenv is no longer active.) At this point, when I run code within Spyder that contains the line

from selenium import webdriver

the Spyder console reports

ModuleNotFoundError: No module named 'selenium'

My questions are:

Is Spyder really running in testenv? If so, why is this error being reported? If not, what am I doing wrong?

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EDIT: Further research turned up the aptly-named thread "Spyder does not run in Anaconda virtual environment on Windows 10". I followed the suggestion, in the accepted answer, of installing Spyder after activating the environment, but that just returned the message

# All requested packages already installed.
# packages in environment at C:\Anaconda3\envs\testenv:
#
spyder                    3.2.2                    py36_0

One of that answer's comments suggests using where spyder within the active environment to check which executables are available. This returned

C:\Anaconda3\Scripts\spyder.exe
C:\Anaconda3\envs\testenv\Scripts\spyder.exe

So I tried starting Spyder by typing the full path of the second entry. Spyder opened, and my program ran without errors. This seems to have solved the problem.

Answer 1

I issued the command where spyder within the active environment to check the locations of Spyder's executables. This returned

C:\Anaconda3\Scripts\spyder.exe
C:\Anaconda3\envs\testenv\Scripts\spyder.exe

So I started Spyder by typing the full path of the second entry, and my program ran without errors.