Update unit tests to fit "no default master branch" of poetry-core#192

Author: grimmerk

tests/installation/test_installer.py

@@ -2062,7 +2062,8 @@ def test_installer_uses_prereleases_if_they_are_compatible(
     package.python_versions = "~2.7 || ^3.4"
     package.add_dependency(
         Factory.create_dependency(
-            "prerelease", {"git": "https://github.com/demo/prerelease.git"}
+            "prerelease",
+            {"git": "https://github.com/demo/prerelease.git", "rev": "main"},
         )
     )
 

tests/installation/test_installer_old.py

@@ -1710,7 +1710,8 @@ def test_installer_uses_prereleases_if_they_are_compatible(
     package.python_versions = "~2.7 || ^3.4"
     package.add_dependency(
         Factory.create_dependency(
-            "prerelease", {"git": "https://github.com/demo/prerelease.git"}
+            "prerelease",
+            {"git": "https://github.com/demo/prerelease.git", "rev": "main"},
         )
     )
 

tests/puzzle/test_solver.py

@@ -1227,7 +1227,10 @@ def test_solver_can_resolve_git_dependencies(solver, repo, package):
     repo.add_package(cleo)
 
     package.add_dependency(
-        Factory.create_dependency("demo", {"git": "https://github.com/demo/demo.git"})
+        Factory.create_dependency(
+            "demo",
+            {"git": "https://github.com/demo/demo.git", "rev": DEFAULT_SOURCE_REF},
+        )
     )
 
     transaction = solver.solve()
@@ -1598,7 +1601,10 @@ def test_solver_git_dependencies_update(solver, repo, package, installed):
     installed.add_package(demo_installed)
 
     package.add_dependency(
-        Factory.create_dependency("demo", {"git": "https://github.com/demo/demo.git"})
+        Factory.create_dependency(
+            "demo",
+            {"git": "https://github.com/demo/demo.git", "rev": DEFAULT_SOURCE_REF},
+        )
     )
 
     transaction = solver.solve()