ci: coalesce tests to avoid increasing test durations

Author: consideRatio

tests/julia/README.md

@@ -13,11 +13,13 @@
 - Tests use of a `Project.toml` file for Julia, using the repo2docker default
   version of Julia as specified in `julia_project.py`.
 
-### project-1.0.2
+### project-1.0.2-binder-dir
 
 - Tests use of a `Project.toml` file for Julia, using a version of Julia
   specified via `julia = "=1.0.2"` in `Project.toml`'s `[compat]` section.
 
+- Test use of a `.binder` directory.
+
 ### require
 
 - Tests use of a `REQUIRE` file for Julia, using the repo2docker default version

tests/julia/project-1.0.2/Project.toml renamed to tests/julia/project-1.0.2-binder-dir/.binder/Project.toml

@@ -0,0 +1,8 @@
+# A broken Project.toml, but the idea is that the test should ignore this file
+# anyhow as there is a .binder folder.
+#
+[deps]
+IteratorInterfaceExtensions = "invalid"
+
+[compat]
+julia = "=1.0.invalid"