atlas tool: testing via mocking (#18588)

* atlas: refactoring
* Atlas: do some basic testing via mocking

tools/atlas/tests/testes.nimble

@@ -0,0 +1,23 @@
+version = "1.0.0"
+author = "disruptek"
+description = "a cure for salty testes"
+license = "MIT"
+
+#requires "cligen >= 0.9.41 & <= 0.9.45"
+#requires "bump >= 1.8.18 & < 2.0.0"
+requires "https://github.com/disruptek/grok >= 0.0.4 & < 1.0.0"
+requires "https://github.com/juancarlospaco/nim-bytes2human"
+
+bin = @["testes"]           # build the binary for basic test running
+installExt = @["nim"]       # we need to install testes.nim also
+skipDirs = @["tests"]       # so stupid...  who doesn't want tests?
+
+task test, "run tests for ci":
+  exec "nim c --run testes.nim"
+
+task demo, "produce a demo":
+  when (NimMajor, NimMinor) != (1, 0):
+    echo "due to nim bug #16307, use nim-1.0"
+    quit 1
+  exec """demo docs/demo.svg "nim c --out=\$1 examples/balls.nim""""
+  exec """demo docs/clean.svg "nim c --define:danger --out=\$1 tests/testicles.nim""""