Add some basic unit tests for the following files: (#1050)

* Add some basic unit tests for cluster, kube-auth-proxy, and kubeconfig-manager

- src/main/cluster.ts
- src/main/kube-auth-proxy.ts
- src/main/kubeconfig-manager.ts

Signed-off-by: Sebastian Malton <sebastian@malton.name>

yarn.lock

@@ -7080,6 +7080,13 @@ jest-message-util@^26.0.1:
     slash "^3.0.0"
     stack-utils "^2.0.2"
 
+jest-mock-extended@^1.0.10:
+  version "1.0.10"
+  resolved "https://registry.yarnpkg.com/jest-mock-extended/-/jest-mock-extended-1.0.10.tgz#a4b1f5b0bb1121acf7c58cd5423d04c473532702"
+  integrity sha512-R2wKiOgEUPoHZ2kLsAQeQP2IfVEgo3oQqWLSXKdMXK06t3UHkQirA2Xnsdqg/pX6KPWTsdnrzE2ig6nqNjdgVw==
+  dependencies:
+    ts-essentials "^4.0.0"
+
 jest-mock@^26.0.1:
   version "26.0.1"
   resolved "https://registry.yarnpkg.com/jest-mock/-/jest-mock-26.0.1.tgz#7fd1517ed4955397cf1620a771dc2d61fad8fd40"
@@ -11382,6 +11389,11 @@ truncate-utf8-bytes@^1.0.0:
   dependencies:
     utf8-byte-length "^1.0.1"
 
+ts-essentials@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/ts-essentials/-/ts-essentials-4.0.0.tgz#506c42b270bbd0465574b90416533175b09205ab"
+  integrity sha512-uQJX+SRY9mtbKU+g9kl5Fi7AEMofPCvHfJkQlaygpPmHPZrtgaBqbWFOYyiA47RhnSwwnXdepUJrgqUYxoUyhQ==
+
 ts-jest@^26.1.0:
   version "26.3.0"
   resolved "https://registry.yarnpkg.com/ts-jest/-/ts-jest-26.3.0.tgz#6b2845045347dce394f069bb59358253bc1338a9"