diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_prompt_preset_selector.py b/tests/test_prompt_preset_selector.py
new file mode 100644
index 0000000..546aa06
--- /dev/null
+++ b/tests/test_prompt_preset_selector.py
@@ -0,0 +1,149 @@
+import pytest
+from src.nodes.prompt_preset_selector import PromptPresetSelector
+
+
+@pytest.fixture
+def node():
+    return PromptPresetSelector()
+
+
+def run(node, text, index=0, on_error="strict", cleanup=False):
+    return node.process(
+        text=text,
+        preset_index=index,
+        open_tag="{%",
+        close_tag="%}",
+        separator="|",
+        on_error=on_error,
+        cleanup=cleanup,
+    )
+
+
+# --- Base cases ---
+
+
+def test_simple_index_0(node):
+    text, idx, count = run(node, "I am {% happy | sad %} today")
+    assert text == "I am happy today"
+    assert idx == 0
+    assert count == 2
+
+
+def test_simple_index_1(node):
+    text, _, _ = run(node, "I am {% happy | sad %} today", index=1)
+    assert text == "I am sad today"
+
+
+def test_empty_preset_first(node):
+    text, _, count = run(node, "I am {% | sad %} today", index=0)
+    assert text == "I am  today"
+    assert count == 2
+
+
+def test_empty_preset_second(node):
+    text, _, _ = run(node, "I am {% happy | %} today", index=1)
+    assert text == "I am  today"
+
+
+def test_multiple_blocks_same_index(node):
+    text, _, count = run(node, "{% a | b %} and {% c | d %}", index=1)
+    assert text == "b and d"
+    assert count == 2
+
+
+def test_no_blocks(node):
+    text, idx, count = run(node, "clean text")
+    assert text == "clean text"
+    assert count == 0
+
+
+def test_three_presets(node):
+    text, _, count = run(node, "{% a | b | c %}", index=2)
+    assert text == "c"
+    assert count == 3
+
+
+# --- Mode strict ---
+
+
+def test_strict_index_out_of_range(node):
+    with pytest.raises(ValueError, match="out of range"):
+        run(node, "{% a | b %}", index=5, on_error="strict")
+
+
+def test_strict_inconsistent_counts(node):
+    with pytest.raises(ValueError, match="inconsistent"):
+        run(node, "{% a | b %} and {% c | d | e %}", on_error="strict")
+
+
+# --- Mode clamp ---
+
+
+def test_clamp_index_out_of_range(node):
+    text, _, _ = run(node, "{% a | b %}", index=5, on_error="clamp")
+    assert text == "b"
+
+
+def test_clamp_inconsistent_uses_last(node):
+    # bloc 1 with 2 options, bloc 2 with 3 — index 2 clamp on bloc 1
+    text, _, _ = run(node, "{% a | b %} and {% c | d | e %}", index=2, on_error="clamp")
+    assert text == "b and e"
+
+
+# --- Mode empty ---
+
+
+def test_empty_index_out_of_range(node):
+    text, _, _ = run(node, "{% a | b %}", index=5, on_error="empty")
+    assert text == ""
+
+
+# --- Custom tags / separator ---
+
+
+def test_custom_tags(node):
+    result, _, _ = node.process(
+        text="I am << happy / sad >> today",
+        preset_index=1,
+        open_tag="<<",
+        close_tag=">>",
+        separator="/",
+        on_error="strict",
+        cleanup=False,
+    )
+    assert result == "I am sad today"
+
+
+# --- Cleanup ---
+
+
+def test_cleanup_double_comma(node):
+    text, _, _ = run(node, "tag1, {% a | %}, tag2", index=1, cleanup=True)
+    assert text == "tag1, tag2"
+
+
+# --- VALIDATE_INPUTS ---
+
+
+def test_validate_empty_separator():
+    result = PromptPresetSelector.VALIDATE_INPUTS(
+        open_tag="{%",
+        close_tag="%}",
+        separator="",
+        on_error="strict",
+        cleanup=True,
+        text="",
+    )
+    assert result != True
+
+
+def test_validate_same_tags():
+    result = PromptPresetSelector.VALIDATE_INPUTS(
+        open_tag="%%",
+        close_tag="%%",
+        separator="|",
+        on_error="strict",
+        cleanup=True,
+        text="",
+    )
+    assert result != True