CI: run doctests to catch regressions

Run it only against the Julia LTS release, as outputs may differ
between Julia releases.

Author: fingolfin

.github/workflows/CI.yml

@@ -22,6 +22,7 @@ jobs:
       matrix:
         version:
           - '1.6'
+          - 'lts'
           - '1'
 #          - 'nightly'
         os:
@@ -48,6 +49,17 @@ jobs:
       - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
+      - name: "Run doctests"
+        if: ${{ matrix.version == 'lts' }} # only run in one Julia version due to fluctuations
+        run: |
+          julia --project=docs --color=yes --code-coverage -e '
+            using Pkg
+            Pkg.develop(PackageSpec(path=pwd()))
+            Pkg.instantiate()
+            using Documenter
+            using DataStructures
+            DocMeta.setdocmeta!(DataStructures, :DocTestSetup, :(using DataStructures); recursive=true)
+            doctest(DataStructures)'
       - uses: julia-actions/julia-processcoverage@v1
       - uses: codecov/codecov-action@v5
         with: