fix compare tests (#229)

The compare tests failed if the commits on master branch were merge commits.
This fixes the tests by checking the latest commit on master branch and changing the test conditions accordingly.

---------

Co-authored-by: Dilum Aluthge <[email protected]>

Author: tanmaykm

test/read_only_api_tests.jl

@@ -86,10 +86,21 @@ end
     @test hasghobj("master", first(branches(ghjl; auth = auth)))
 
     # test GitHub.compare
-    @test compare(ghjl, "master", "master~"; auth = auth).behind_by == 1
-    let comparison = compare(ghjl, "master~", "master"; auth = auth)
-        @test comparison.ahead_by == 1
-        @test length(comparison.commits) == 1
+    # check if the latest commit is a merge commit
+    latest_commit = GitHub.branch(ghjl, "master"; auth=auth).commit
+    is_latest_commit_merge = length(latest_commit.parents) > 1
+    if is_latest_commit_merge
+        @test compare(ghjl, "master", "master~"; auth = auth).behind_by >= 1
+        let comparison = compare(ghjl, "master~", "master"; auth = auth)
+            @test comparison.ahead_by >= 1
+            @test length(comparison.commits) >= 1
+        end
+    else
+        @test compare(ghjl, "master", "master~"; auth = auth).behind_by == 1
+        let comparison = compare(ghjl, "master~", "master"; auth = auth)
+            @test comparison.ahead_by == 1
+            @test length(comparison.commits) == 1
+        end
     end
 
     # test GitHub.file, GitHub.directory, GitHub.readme, GitHub.permalink