Add some tests for package remove

tests/reftests/basic.test

@@ -0,0 +1,48 @@
+N0REP0
+### :::::: removal of partial dependencies (#4727)
+### <pkg:a.1>
+opam-version: "2.0"
+### <pkg:b.1>
+opam-version: "2.0"
+### <pkg:c.1>
+opam-version: "2.0"
+depends: "a" | "b"
+### opam switch create default --empty
+### opam install a b c
+The following actions will be performed:
+  - install b 1
+  - install a 1
+  - install c 1
+===== 3 to install =====
+
+<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+-> installed a.1
+-> installed b.1
+-> installed c.1
+Done.
+### opam remove a --show
+The following actions would be performed:
+  - remove    a 1
+  - recompile c 1 [uses a]
+===== 1 to recompile | 1 to remove =====
+### opam remove --auto --show
+Nothing to do.
+### opam remove a --auto --show
+The following actions would be performed:
+  - remove c 1 [uses a]
+  - remove a 1
+===== 2 to remove =====
+### :::::: message on removal of an unavailable package (#4890)
+### <pkg:z.1>
+opam-version: "2.0"
+available: false
+### <pkg:w.1>
+opam-version: "2.0"
+depends: "z"
+### opam remove z
+[ERROR] z: unmet availability conditions: 'false'
+# Return code 5 #
+### opam remove w
+[NOTE] w is not installed.
+
+Nothing to do.

tests/reftests/dune.inc

@@ -16,6 +16,23 @@
    %{targets}
    (run ./run.exe %{bin:opam} %{dep:avoid-version.test} %{read-lines:testing-env}))))
 
+(rule
+ (alias reftest-basic)
+ (action
+  (diff basic.test basic.out)))
+
+(alias
+ (name reftest)
+ (deps (alias reftest-basic)))
+
+(rule
+ (targets basic.out)
+ (deps root-N0REP0)
+ (action
+  (with-stdout-to
+   %{targets}
+   (run ./run.exe %{bin:opam} %{dep:basic.test} %{read-lines:testing-env}))))
+
 (rule
  (alias reftest-cli-versioning)
  (action