Add initial test framework for utils functions

Added the initial test framework that will eventually encompass all of the functions in the package. Started with the primary utility functions since those are widely used and also simple enough to get used to writing tests. All current tests pass 😁

tests/test_utils.py

+import pytest
+from typing import Literal
+from pathlib import Path
+from rc_gpfs import utils
+
+
+@pytest.mark.parametrize("path", ["/data/rc/gpfs-policy", Path("/data/rc/gpfs-policy")])
+def test_as_path_valid(path: Path | Literal["/data/rc/gpfs-policy"]):
+    p_path = utils.as_path(path)
+    assert isinstance(p_path, Path)
+
+@pytest.mark.parametrize(
+    "value,unit,to_unit,use_binary,expected",
+    [
+        (1,"G","K",False,1000000),
+        (4,'K','base',True,4096),
+        ('100','base','T',False,1e-10)
+    ]
+)
+def test_convert_si(value,unit,to_unit,use_binary,expected):
+    assert utils.convert_si(value,unit,to_unit,use_binary) == expected
+
+@pytest.mark.parametrize(
+    "val,default,expected",
+    [
+        ('1 kiB',None,1024),
+        ('1 kiB',(1024**4),1024),
+        ('10 TiB',None,10*(1024**4)),
+        (None,1024,1024),
+        (None,None,None),
+        ('1.5 MiB',None,1572864)
+    ]
+)
+def test_as_bytes(val,default,expected):
+    assert utils.as_bytes(val,default) == expected
+
+class TestSizeDistribution:
+    inputs = [
+        ["4 KiB", "4 MiB", "1 GiB", "10 GiB", "100 GiB", "1 TiB"],
+        [4096, 4194304, 1073741824, 10737418240, 107374182400, 1099511627776],
+        ["10 GiB", 1024, 4096, "1 KiB",0],
+        "1 MiB"
+    ]
+
+    expected_bins = [
+        [4096, 4194304, 1073741824, 10737418240, 107374182400, 1099511627776],
+        [4096, 4194304, 1073741824, 10737418240, 107374182400, 1099511627776],
+        [1024, 4096, 10737418240],
+        [1048576]
+    ]
+
+    expected_labels = [
+        ["0 B-4 KiB","4 KiB-4 MiB","4 MiB-1 GiB","1 GiB-10 GiB","10 GiB-100 GiB","100 GiB-1 TiB",">1 TiB"],
+        ["0 B-4 KiB","4 KiB-4 MiB","4 MiB-1 GiB","1 GiB-10 GiB","10 GiB-100 GiB","100 GiB-1 TiB",">1 TiB"],
+        ["0 B-1 KiB","1 KiB-4 KiB","4 KiB-10 GiB",">10 GiB"],
+        ["0 B-1 MiB",">1 MiB"]
+    ]
+
+    @pytest.mark.parametrize("bins,expected",list(zip(expected_bins,expected_labels)))
+    def test_create_size_bin_labels(self,bins,expected):
+        assert utils.create_size_bin_labels(bins) == expected
+    
+    @pytest.mark.parametrize("bins,expected",list(zip(inputs,list(zip(expected_bins,expected_labels)))))
+    def test_prep_size_distribution(self,bins,expected):
+        assert utils.prep_size_distribution(size_bins=bins) == expected
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