Extract jvm_version parsing into a testable helper function

Split the version-string-to-tuple conversion out of jvm_version() into
_jvm_version_str_to_tuple() and add unit tests.

Author: ncittm

src/scyjava/_jvm.py

@@ -130,11 +130,15 @@ def jvm_version() -> tuple[int, ...]:
     except subprocess.CalledProcessError as e:
         raise RuntimeError("System call to java failed") from e
 
-    output = output.replace("\n", " ").replace("\r", "")
-    m = re.match('.* version "([^"]*)"', output)
+    return _jvm_version_str_to_tuple(output, java)
+
+
+def _jvm_version_str_to_tuple(java_version_output: str, java: str) -> tuple[int, ...]:
+    java_version_output = java_version_output.replace("\n", " ").replace("\r", "")
+    m = re.match('.* version "([^"]*)"', java_version_output)
     if not m:
         raise RuntimeError(
-            f"Inscrutable java command output:\n$ {java} -version\n{output}"
+            f"Inscrutable java command output:\n$ {java} -version\n{java_version_output}"
         )
 
     v = m.group(1)

tests/test_jvm_version.py

@@ -0,0 +1,15 @@
+"""
+Tests for functions in _versions submodule.
+"""
+
+from scyjava._jvm import _jvm_version_str_to_tuple
+
+
+def test_jvm_version():
+    assert _jvm_version_str_to_tuple(' version "17.0.1"', "java") == (17, 0, 1)
+    assert _jvm_version_str_to_tuple(' version "17.0.18-internal"', "java") == (
+        17, 0, 18)
+    assert _jvm_version_str_to_tuple(' version "11.0.9.1-internal"', "java") == (
+        11, 0, 9, 1)
+    assert _jvm_version_str_to_tuple(' version "1.8.0_312"', "java") == (1, 8, 0)
+    assert _jvm_version_str_to_tuple(' version "25"', "java") == (25,)