test: use filename string instead of pathlib.Path to fix tests using diffpy.structure

Author: ycexiao

news/use-string-in-structure

@@ -0,0 +1,23 @@
+**Added:**
+
+* No news added: Use filename string instead of pathlib.Path to fix the test using ``diffpy.structure``.
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

tests/test_pdf.py

@@ -160,6 +160,7 @@ def testGenerator(
 
     stru = PDFFitStructure()
     ciffile = datafile("ni.cif")
+    ciffile = str(ciffile)
     stru.read(ciffile)
     for i in range(4):
         stru[i].Bisoequiv = 1
@@ -298,7 +299,9 @@ def test_pickling(
 
     pc = PDFContribution("pdf")
     pc.loadData(datafile("ni-q27r100-neutron.gr"))
-    ni = loadStructure(datafile("ni.cif"))
+    ciffile = datafile("ni.cif")
+    ciffile = str(ciffile)
+    ni = loadStructure(ciffile)
     ni.Uisoequiv = 0.003
     pc.addStructure("ni", ni)
     pc.setCalculationRange(0, 10)