diff --git a/pipenv/utils/funktools.py b/pipenv/utils/funktools.py
index edcfc78b..f1a682cc 100644
--- a/pipenv/utils/funktools.py
+++ b/pipenv/utils/funktools.py
@@ -70,3 +70,11 @@ def unnest(elem: Iterable) -> Any:
                     yield sub
             else:
                 yield el
+
+
+def dedup(iterable: Iterable) -> Iterable:
+    # type: (Iterable) -> Iterable
+    """Deduplicate an iterable object like iter(set(iterable)) but order-
+    preserved."""
+
+    return iter(dict.fromkeys(iterable))
diff --git a/tests/unit/test_funktools.py b/tests/unit/test_funktools.py
new file mode 100644
index 00000000..39c7b3ec
--- /dev/null
+++ b/tests/unit/test_funktools.py
@@ -0,0 +1,50 @@
+import pytest
+
+from pipenv.utils.funktools import dedup, unnest, _is_iterable
+
+
+def test_unnest():
+    nested_iterable = (
+            1234, (3456, 4398345, (234234)), (
+                2396, (
+                    928379, 29384, (
+                        293759, 2347, (
+                            2098, 7987, 27599
+                        )
+                    )
+                )
+            )
+        )
+    list(unnest(nested_iterable)) == [1234, 3456, 4398345, 234234,
+                                      2396, 928379, 29384, 293759,
+                                      2347, 2098, 7987, 27599]
+
+
+@pytest.mark.parametrize(
+    "iterable, result",
+    [
+        [["abc", "def"], True],
+        [("abc", "def"), True],
+        ["abcdef", True],
+        [None, False],
+        [1234, False],
+    ],
+)
+def test_is_iterable(iterable, result):
+    assert _is_iterable(iterable) is result
+
+
+def test_unnest_none():
+    assert list(unnest(None)) == [None]
+
+
+def test_dedup():
+    dup_strings = ["abcde", "fghij", "klmno", "pqrst", "abcde", "klmno"]
+    assert list(dedup(dup_strings)) == [
+        "abcde",
+        "fghij",
+        "klmno",
+        "pqrst",
+    ]
+    dup_ints = (12345, 56789, 12345, 54321, 98765, 54321)
+    assert list(dedup(dup_ints)) == [12345, 56789, 54321, 98765]