diff --git a/CHANGELOG.md b/CHANGELOG.md
index dd2a6bb..002b9fb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,9 @@ Contributors add user-facing entries under `[Unreleased]` in the same PR. Mainta
 
 ## [Unreleased]
 
+### Added
+- **Tests**: Backfilled `test_skill.py` for six registry skills (`mica_module`, `pii_masker`, `synthetic_generator`, `wallet_screening`, `pdf_form_filler`, `prompt_rewriter`); all registry skills now ship co-located bundle tests. Fixed `prompt_rewriter` package export so pytest can collect the bundle (#158).
+
 ### Changed
 - **CI**: CodeQL GitHub Action upgraded from v3 to v4.
 - **Dependencies**: Extended `[all]` with registry skill runtime deps (`web3`, `fastembed`, `numpy`); added `[defi]` and `[embeddings]` optional extras. Documented manifest ↔ `pyproject.toml` convention in CONTRIBUTING and TESTING.md.
diff --git a/skills/compliance/mica_module/test_skill.py b/skills/compliance/mica_module/test_skill.py
new file mode 100644
index 0000000..cf9575e
--- /dev/null
+++ b/skills/compliance/mica_module/test_skill.py
@@ -0,0 +1,67 @@
+import os
+
+import pytest
+import yaml
+
+from .skill import MiCAModuleSkill
+
+
+@pytest.fixture
+def skill():
+    return MiCAModuleSkill()
+
+
+@pytest.fixture
+def manifest():
+    manifest_path = os.path.join(os.path.dirname(__file__), "manifest.yaml")
+    with open(manifest_path, "r", encoding="utf-8") as f:
+        return yaml.safe_load(f)
+
+
+def test_skill_manifest_consistency(skill, manifest):
+    skill_manifest = skill.manifest
+    assert skill_manifest["name"] == manifest["name"]
+    assert skill_manifest["version"] == manifest["version"]
+
+
+def test_stateless_rag_execution(skill):
+    result = skill.execute(
+        {
+            "user_prompt": (
+                "I want to issue an asset-referenced token. "
+                "What are the authorization rules?"
+            ),
+            "run_evaluator": False,
+        }
+    )
+    assert result["policy_status"] == "CAUTION"
+    assert "retrieved_sections" in result
+    assert "final_context_for_agent" in result
+    assert "Evaluator disabled" in result["gemini_evaluator_feedback"]["holes_found"]
+
+
+def test_router_normalization(skill):
+    mock_corpus = [
+        {
+            "title_num": "Title V",
+            "article_num": "Article 59",
+            "keywords": ["authorisation", "casp"],
+            "content": "CASP Authorization rules...",
+        }
+    ]
+    matched = skill._route_and_fetch("Authorization of a CASP", mock_corpus)
+    assert len(matched) > 0
+    assert matched[0]["article_num"] == "Article 59"
+
+
+def test_router_deduplication(skill):
+    mock_corpus = [
+        {
+            "title_num": "Title V",
+            "article_num": "Article 59",
+            "keywords": ["authorisation", "casp"],
+            "content": "CASP Authorization rules...",
+        }
+    ]
+    matched = skill._route_and_fetch("authorisation casp", mock_corpus)
+    assert len(matched) == 1
diff --git a/skills/compliance/pii_masker/test_skill.py b/skills/compliance/pii_masker/test_skill.py
new file mode 100644
index 0000000..736d7b2
--- /dev/null
+++ b/skills/compliance/pii_masker/test_skill.py
@@ -0,0 +1,58 @@
+import os
+
+import pytest
+import yaml
+
+from .skill import PIIMaskerSkill
+
+
+@pytest.fixture
+def skill():
+    return PIIMaskerSkill()
+
+
+@pytest.fixture
+def manifest():
+    manifest_path = os.path.join(os.path.dirname(__file__), "manifest.yaml")
+    with open(manifest_path, "r", encoding="utf-8") as f:
+        return yaml.safe_load(f)
+
+
+def test_skill_manifest_consistency(skill, manifest):
+    skill_manifest = skill.manifest
+    assert skill_manifest["name"] == manifest["name"]
+    assert skill_manifest["version"] == manifest["version"]
+
+
+def test_pii_masker_modes(mocker, skill):
+    mock_response = (
+        "Hello [PERSON_1], your wallet [CRYPTO_ADDRESS] and [EMAIL] have been verified."
+    )
+    mocker.patch.object(
+        skill,
+        "_call_ollama",
+        return_value=(mock_response, ["PERSON_1", "CRYPTO_ADDRESS", "EMAIL"]),
+    )
+
+    sample_text = (
+        "Hello John Doe, your wallet 0xabc and john@doe.com have been verified."
+    )
+
+    result_mask = skill.execute({"text": sample_text})
+    assert (
+        result_mask["sanitized_text"]
+        == "Hello [PERSON_1], your wallet [CRYPTO_ADDRESS] and [EMAIL] have been verified."
+    )
+    assert "PERSON" in result_mask["metadata"]["detected_entities"]
+    assert "CRYPTO_ADDRESS" in result_mask["metadata"]["detected_entities"]
+
+    result_redact = skill.execute({"text": sample_text, "mode": "redact"})
+    assert (
+        result_redact["sanitized_text"]
+        == "Hello XXXX, your wallet XXXX and XXXX have been verified."
+    )
+
+    result_remove = skill.execute({"text": sample_text, "mode": "remove"})
+    assert (
+        result_remove["sanitized_text"] == "Hello , your wallet and have been verified."
+    )
diff --git a/skills/data_engineering/synthetic_generator/test_skill.py b/skills/data_engineering/synthetic_generator/test_skill.py
new file mode 100644
index 0000000..dba8d7a
--- /dev/null
+++ b/skills/data_engineering/synthetic_generator/test_skill.py
@@ -0,0 +1,58 @@
+import os
+
+import pytest
+import yaml
+
+from .skill import SyntheticGeneratorSkill
+
+
+@pytest.fixture
+def skill():
+    return SyntheticGeneratorSkill()
+
+
+@pytest.fixture
+def manifest():
+    manifest_path = os.path.join(os.path.dirname(__file__), "manifest.yaml")
+    with open(manifest_path, "r", encoding="utf-8") as f:
+        return yaml.safe_load(f)
+
+
+def test_skill_manifest_consistency(skill, manifest):
+    skill_manifest = skill.manifest
+    assert skill_manifest["name"] == manifest["name"]
+    assert skill_manifest["version"] == manifest["version"]
+
+
+def test_entropy_score(skill):
+    low_entropy_text = "test " * 100
+    score_low = skill._calculate_entropy_score(low_entropy_text)
+
+    high_text = "The brown fox jumps over the dog. Programming is fun!"
+    score_high = skill._calculate_entropy_score(high_text)
+
+    assert score_high > score_low
+
+
+def test_execute_success(mocker, skill):
+    mock_json_response = """```json
+[
+  {"instruction": "x", "input": "y", "output": "z"}
+]
+```"""
+    mocker.patch.object(skill, "_call_gemini", return_value=mock_json_response)
+
+    result = skill.execute(
+        {
+            "domain": "test domain",
+            "num_samples": 1,
+            "diversity_prompt": "be diverse",
+            "model_provider": "gemini",
+        }
+    )
+
+    assert result["status"] == "success"
+    assert result["provider_used"] == "gemini"
+    assert result["samples_generated"] == 1
+    assert "samples" in result
+    assert result["samples"][0]["instruction"] == "x"
diff --git a/skills/finance/wallet_screening/test_skill.py b/skills/finance/wallet_screening/test_skill.py
new file mode 100644
index 0000000..9ec4fab
--- /dev/null
+++ b/skills/finance/wallet_screening/test_skill.py
@@ -0,0 +1,83 @@
+import os
+from unittest.mock import MagicMock, patch
+
+import pytest
+import yaml
+
+from .skill import WalletScreeningSkill
+
+
+@pytest.fixture
+def skill():
+    return WalletScreeningSkill()
+
+
+@pytest.fixture
+def manifest():
+    manifest_path = os.path.join(os.path.dirname(__file__), "manifest.yaml")
+    with open(manifest_path, "r", encoding="utf-8") as f:
+        return yaml.safe_load(f)
+
+
+def test_manifest_schema(manifest):
+    assert manifest["name"] == "wallet_screening"
+    assert "address" in manifest["parameters"]["properties"]
+
+
+def test_invalid_address(skill):
+    result = skill.execute({"address": "invalid_addr"})
+    assert "error" in result
+    assert "Invalid Ethereum address" in result["error"]
+
+
+def test_missing_api_key(skill):
+    skill.etherscan_api_key = None
+    result = skill.execute({"address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"})
+    assert "error" in result
+    assert "Missing ETHERSCAN_API_KEY" in result["error"]
+
+
+@patch("skills.finance.wallet_screening.skill.requests.get")
+def test_execute_success(mock_get, skill):
+    skill.etherscan_api_key = "dummy_key"
+
+    mock_eth_balance = MagicMock()
+    mock_eth_balance.json.return_value = {
+        "status": "1",
+        "result": "1000000000000000000",
+    }
+
+    mock_txs = MagicMock()
+    mock_txs.json.return_value = {
+        "status": "1",
+        "result": [
+            {
+                "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045".lower(),
+                "to": "0x123",
+                "value": "500000000000000000",
+                "isError": "0",
+                "gasUsed": "21000",
+                "gasPrice": "1000000000",
+            }
+        ],
+    }
+
+    mock_price = MagicMock()
+    mock_price.json.return_value = {"ethereum": {"usd": 2000.0, "eur": 1800.0}}
+
+    def get_side_effect(url, **kwargs):
+        params = kwargs.get("params") or {}
+        if params.get("action") == "balance":
+            return mock_eth_balance
+        if params.get("action") == "txlist":
+            return mock_txs
+        return mock_price
+
+    mock_get.side_effect = get_side_effect
+
+    result = skill.execute({"address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"})
+
+    assert "error" not in result
+    assert "summary" in result
+    assert result["summary"]["balance_eth"] == 1.0
+    assert result["summary"]["balance_usd"] == 2000.0
diff --git a/skills/office/pdf_form_filler/test_skill.py b/skills/office/pdf_form_filler/test_skill.py
new file mode 100644
index 0000000..b2d1940
--- /dev/null
+++ b/skills/office/pdf_form_filler/test_skill.py
@@ -0,0 +1,84 @@
+import os
+from unittest.mock import MagicMock, patch
+
+import fitz
+import pytest
+import yaml
+
+from .skill import PDFFormFillerSkill
+
+
+@pytest.fixture
+def skill():
+    return PDFFormFillerSkill()
+
+
+@pytest.fixture
+def manifest():
+    manifest_path = os.path.join(os.path.dirname(__file__), "manifest.yaml")
+    with open(manifest_path, "r", encoding="utf-8") as f:
+        return yaml.safe_load(f)
+
+
+def test_skill_manifest_consistency(skill, manifest):
+    skill_manifest = skill.manifest
+    assert skill_manifest["name"] == manifest["name"]
+    assert skill_manifest["version"] == manifest["version"]
+
+
+def test_missing_pdf_returns_error(skill):
+    result = skill.execute(
+        {
+            "pdf_path": "/nonexistent/form.pdf",
+            "instructions": "Fill name with Alice",
+        }
+    )
+    assert "error" in result
+    assert "PDF file not found" in result["error"]
+
+
+def test_missing_instructions_returns_error(skill, tmp_path):
+    pdf_path = tmp_path / "blank.pdf"
+    doc = fitz.open()
+    doc.new_page()
+    doc.save(str(pdf_path))
+    doc.close()
+
+    result = skill.execute({"pdf_path": str(pdf_path), "instructions": ""})
+    assert "error" in result
+    assert "No instructions provided" in result["error"]
+
+
+@patch("skills.office.pdf_form_filler.skill.anthropic.Anthropic")
+def test_execute_mocked(mock_anthropic_cls, tmp_path):
+    mock_client = mock_anthropic_cls.return_value
+    mock_message = MagicMock()
+    mock_message.content = [MagicMock(text='{"page0_test_field": "Hello World"}')]
+    mock_client.messages.create.return_value = mock_message
+
+    skill = PDFFormFillerSkill()
+
+    pdf_path = tmp_path / "form.pdf"
+    doc = fitz.open()
+    page = doc.new_page()
+    widget = fitz.Widget()
+    widget.rect = fitz.Rect(10, 10, 100, 30)
+    widget.field_name = "test_field"
+    widget.field_type = 7
+    page.add_widget(widget)
+    doc.save(str(pdf_path))
+    doc.close()
+
+    result = skill.execute(
+        {
+            "pdf_path": str(pdf_path),
+            "instructions": "Fill test field with Hello World",
+        }
+    )
+
+    assert result["status"] == "success"
+    assert "page0_test_field" in result["filled_fields"]
+    assert os.path.exists(result["output_path"])
+
+    if os.path.exists(result["output_path"]):
+        os.remove(result["output_path"])
diff --git a/skills/optimization/prompt_rewriter/__init__.py b/skills/optimization/prompt_rewriter/__init__.py
index d479929..265a85e 100644
--- a/skills/optimization/prompt_rewriter/__init__.py
+++ b/skills/optimization/prompt_rewriter/__init__.py
@@ -1,3 +1,3 @@
-from .skill import MyAwesomeSkill
+from .skill import PromptRewriter
 
-__all__ = ["MyAwesomeSkill"]
+__all__ = ["PromptRewriter"]
diff --git a/skills/optimization/prompt_rewriter/test_skill.py b/skills/optimization/prompt_rewriter/test_skill.py
new file mode 100644
index 0000000..07f3cbf
--- /dev/null
+++ b/skills/optimization/prompt_rewriter/test_skill.py
@@ -0,0 +1,55 @@
+import os
+
+import pytest
+import yaml
+
+from .skill import PromptRewriter
+
+
+@pytest.fixture
+def skill():
+    return PromptRewriter()
+
+
+@pytest.fixture
+def manifest():
+    manifest_path = os.path.join(os.path.dirname(__file__), "manifest.yaml")
+    with open(manifest_path, "r", encoding="utf-8") as f:
+        return yaml.safe_load(f)
+
+
+def test_skill_manifest_consistency(skill, manifest):
+    skill_manifest = skill.manifest
+    assert skill_manifest["name"] == manifest["name"]
+    assert skill_manifest["version"] == manifest["version"]
+
+
+def test_rewriter_execution_low(skill):
+    result = skill.execute(
+        {
+            "raw_text": "This   is a    very\n\n\nspaced out  prompt.",
+            "compression_aggression": "low",
+        }
+    )
+    assert result["compressed_text"] == "This is a very spaced out prompt."
+    assert result["original_tokens"] >= result["new_tokens"]
+
+
+def test_rewriter_execution_high(skill):
+    result = skill.execute(
+        {
+            "raw_text": "Please make sure to read this and analyze the data.",
+            "compression_aggression": "high",
+        }
+    )
+    assert "Please" not in result["compressed_text"]
+    assert "make sure to" not in result["compressed_text"]
+    assert result["tokens_saved"] > 0
+    assert "new_tokens" in result
+    assert "original_tokens" in result
+
+
+def test_empty_string_returns_error(skill):
+    result = skill.execute({"raw_text": ""})
+    assert "error" in result
+    assert result["error"] == "raw_text cannot be empty."