Standardize to use TUSK_RECORDING_SAMPLING_RATE

jy-tan · jy-tan · commit a99019e678e8 · 2026-04-10T14:03:16.000-07:00
diff --git a/docs/environment-variables.md b/docs/environment-variables.md
@@ -110,7 +110,7 @@ Your Tusk Drift API key, required when using Tusk Cloud for storing and managing
 
   This will securely store your auth key for future replay sessions.
 
-## TUSK_SAMPLING_RATE
+## TUSK_RECORDING_SAMPLING_RATE
 
 Controls the base recording rate used during trace collection.
 
@@ -123,14 +123,16 @@ Controls the base recording rate used during trace collection.
 
 ```bash
 # Record all requests (100%)
-TUSK_SAMPLING_RATE=1.0 python app.py
+TUSK_RECORDING_SAMPLING_RATE=1.0 python app.py
 
 # Record 10% of requests
-TUSK_SAMPLING_RATE=0.1 python app.py
+TUSK_RECORDING_SAMPLING_RATE=0.1 python app.py
 ```
 
 If `recording.sampling.mode: adaptive` is enabled in `.tusk/config.yaml`, this environment variable still only changes the base rate; adaptive load shedding remains active.
 
+`TUSK_RECORDING_SAMPLING_RATE` is the canonical variable, but `TUSK_SAMPLING_RATE` is still accepted as a backward-compatible alias.
+
 For more details on sampling rate configuration methods and precedence, see the [Initialization Guide](./initialization.md#configure-sampling-rate).
 
 ## Rust Core Flags
diff --git a/docs/initialization.md b/docs/initialization.md
@@ -74,7 +74,7 @@ Create an initialization file or add the SDK initialization to your application
       <td><code>sampling_rate</code></td>
       <td><code>float</code></td>
       <td><code>None</code></td>
-      <td>Override the base sampling rate (0.0 - 1.0) for recording. Takes precedence over <code>TUSK_SAMPLING_RATE</code> and config file base-rate settings. Does not change <code>recording.sampling.mode</code>.</td>
+      <td>Override the base sampling rate (0.0 - 1.0) for recording. Takes precedence over <code>TUSK_RECORDING_SAMPLING_RATE</code> and config file base-rate settings. Does not change <code>recording.sampling.mode</code>.</td>
     </tr>
   </tbody>
 </table>
@@ -183,7 +183,8 @@ Sampling configuration is resolved in two layers:
 
 1. **Base rate precedence** (highest to lowest):
    - `TuskDrift.initialize(sampling_rate=...)`
-   - `TUSK_SAMPLING_RATE`
+   - `TUSK_RECORDING_SAMPLING_RATE`
+   - legacy alias `TUSK_SAMPLING_RATE`
    - `.tusk/config.yaml` `recording.sampling.base_rate`
    - `.tusk/config.yaml` legacy `recording.sampling_rate`
    - default base rate `1.0`
@@ -207,16 +208,18 @@ sdk = TuskDrift.initialize(
 
 ### Method 2: Environment Variable
 
-Set the `TUSK_SAMPLING_RATE` environment variable to override the base sampling rate:
+Set the `TUSK_RECORDING_SAMPLING_RATE` environment variable to override the base sampling rate:
 
 ```bash
 # Development - record everything
-TUSK_SAMPLING_RATE=1.0 python app.py
+TUSK_RECORDING_SAMPLING_RATE=1.0 python app.py
 
 # Production - sample 10% of requests
-TUSK_SAMPLING_RATE=0.1 python app.py
+TUSK_RECORDING_SAMPLING_RATE=0.1 python app.py
 ```
 
+`TUSK_SAMPLING_RATE` is still supported as a backward-compatible alias, but new setups should prefer `TUSK_RECORDING_SAMPLING_RATE`.
+
 ### Method 3: Configuration File
 
 Use the nested `recording.sampling` config to choose `fixed` vs `adaptive` mode and set the base/minimum rates.
@@ -276,7 +279,7 @@ recording:
       <td><code>sampling.base_rate</code></td>
       <td><code>float</code></td>
       <td><code>1.0</code></td>
-      <td>The base sampling rate (0.0 - 1.0). This is the preferred config key and can be overridden by <code>TUSK_SAMPLING_RATE</code> or the <code>sampling_rate</code> init parameter.</td>
+      <td>The base sampling rate (0.0 - 1.0). This is the preferred config key and can be overridden by <code>TUSK_RECORDING_SAMPLING_RATE</code> or the <code>sampling_rate</code> init parameter.</td>
     </tr>
     <tr>
       <td><code>sampling.min_rate</code></td>
diff --git a/drift/core/drift_sdk.py b/drift/core/drift_sdk.py
@@ -358,16 +358,20 @@ def _determine_sampling_config(self, init_param: float | None) -> ResolvedSampli
                 base_rate = validated
 
         if base_rate is None:
-            env_rate = os.environ.get("TUSK_SAMPLING_RATE")
-            if env_rate is not None:
+            for env_key in ("TUSK_RECORDING_SAMPLING_RATE", "TUSK_SAMPLING_RATE"):
+                env_rate = os.environ.get(env_key)
+                if env_rate is None:
+                    continue
+
                 try:
                     parsed = float(env_rate)
-                    validated = validate_sampling_rate(parsed, "TUSK_SAMPLING_RATE env var")
+                    validated = validate_sampling_rate(parsed, f"{env_key} env var")
                     if validated is not None:
-                        logger.debug(f"Using sampling rate from env var: {validated}")
+                        logger.debug(f"Using sampling rate from {env_key} env var: {validated}")
                         base_rate = validated
+                        break
                 except ValueError:
-                    logger.warning(f"Invalid TUSK_SAMPLING_RATE env var: {env_rate}")
+                    logger.warning(f"Invalid {env_key} env var: {env_rate}")
 
         if base_rate is None and config_sampling and config_sampling.base_rate is not None:
             validated = validate_sampling_rate(config_sampling.base_rate, "config file recording.sampling.base_rate")
diff --git a/drift/instrumentation/aiohttp/e2e-tests/docker-compose.yml b/drift/instrumentation/aiohttp/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/django/e2e-tests/docker-compose.yml b/drift/instrumentation/django/e2e-tests/docker-compose.yml
@@ -28,6 +28,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/fastapi/e2e-tests/docker-compose.yml b/drift/instrumentation/fastapi/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/flask/e2e-tests/docker-compose.yml b/drift/instrumentation/flask/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/grpc/e2e-tests/docker-compose.yml b/drift/instrumentation/grpc/e2e-tests/docker-compose.yml
@@ -18,6 +18,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/drift/instrumentation/httpx/e2e-tests/docker-compose.yml b/drift/instrumentation/httpx/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/psycopg/e2e-tests/docker-compose.yml b/drift/instrumentation/psycopg/e2e-tests/docker-compose.yml
@@ -38,6 +38,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/drift/instrumentation/psycopg2/e2e-tests/docker-compose.yml b/drift/instrumentation/psycopg2/e2e-tests/docker-compose.yml
@@ -38,6 +38,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/drift/instrumentation/redis/e2e-tests/docker-compose.yml b/drift/instrumentation/redis/e2e-tests/docker-compose.yml
@@ -31,6 +31,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/drift/instrumentation/requests/e2e-tests/docker-compose.yml b/drift/instrumentation/requests/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/urllib/e2e-tests/docker-compose.yml b/drift/instrumentation/urllib/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/instrumentation/urllib3/e2e-tests/docker-compose.yml b/drift/instrumentation/urllib3/e2e-tests/docker-compose.yml
@@ -27,6 +27,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
       - USE_MOCK_EXTERNALS=${USE_MOCK_EXTERNALS:-1}
       - MOCK_SERVER_BASE_URL=${MOCK_SERVER_BASE_URL:-http://mock-upstream:8081}
diff --git a/drift/stack-tests/django-postgres/docker-compose.yml b/drift/stack-tests/django-postgres/docker-compose.yml
@@ -39,6 +39,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/drift/stack-tests/django-redis/docker-compose.yml b/drift/stack-tests/django-redis/docker-compose.yml
@@ -32,6 +32,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/drift/stack-tests/fastapi-postgres/docker-compose.yml b/drift/stack-tests/fastapi-postgres/docker-compose.yml
@@ -38,6 +38,7 @@ services:
       - BENCHMARKS=${BENCHMARKS:-}
       - BENCHMARK_DURATION=${BENCHMARK_DURATION:-10}
       - BENCHMARK_WARMUP=${BENCHMARK_WARMUP:-3}
+      - TUSK_RECORDING_SAMPLING_RATE=${TUSK_RECORDING_SAMPLING_RATE:-}
       - TUSK_SAMPLING_RATE=${TUSK_SAMPLING_RATE:-}
     working_dir: /app
     volumes:
diff --git a/tests/unit/test_drift_sdk.py b/tests/unit/test_drift_sdk.py
@@ -20,7 +20,13 @@ def reset_singleton(self):
         TuskDrift._instance = None
         TuskDrift._initialized = False
         # Clear environment variables
-        env_vars = ["TUSK_DRIFT_MODE", "TUSK_API_KEY", "TUSK_SAMPLING_RATE", "ENV"]
+        env_vars = [
+            "TUSK_DRIFT_MODE",
+            "TUSK_API_KEY",
+            "TUSK_RECORDING_SAMPLING_RATE",
+            "TUSK_SAMPLING_RATE",
+            "ENV",
+        ]
         original_env = {k: os.environ.get(k) for k in env_vars}
         for var in env_vars:
             if var in os.environ:
@@ -121,9 +127,10 @@ def reset_singleton(self):
         """Reset singleton state before each test."""
         TuskDrift._instance = None
         TuskDrift._initialized = False
-        # Clear sampling rate env var
-        if "TUSK_SAMPLING_RATE" in os.environ:
-            del os.environ["TUSK_SAMPLING_RATE"]
+        # Clear sampling rate env vars
+        for env_var in ("TUSK_RECORDING_SAMPLING_RATE", "TUSK_SAMPLING_RATE"):
+            if env_var in os.environ:
+                del os.environ[env_var]
         yield
         TuskDrift._instance = None
         TuskDrift._initialized = False
@@ -137,10 +144,31 @@ def test_uses_init_param_sampling_rate(self, reset_singleton):
 
         assert result == 0.5
 
-    def test_uses_env_var_sampling_rate(self, reset_singleton):
-        """Should use sampling rate from env var if init param not provided."""
+    def test_uses_recording_env_var_sampling_rate(self, reset_singleton):
+        """Should use the canonical recording env var if init param not provided."""
         os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
-        os.environ["TUSK_SAMPLING_RATE"] = "0.25"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "0.25"
+        instance = TuskDrift.get_instance()
+
+        result = instance._determine_sampling_rate(None)
+
+        assert result == 0.25
+
+    def test_uses_legacy_sampling_env_var_as_alias(self, reset_singleton):
+        """Should fall back to the legacy env var for backward compatibility."""
+        os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
+        os.environ["TUSK_SAMPLING_RATE"] = "0.2"
+        instance = TuskDrift.get_instance()
+
+        result = instance._determine_sampling_rate(None)
+
+        assert result == 0.2
+
+    def test_recording_env_var_takes_precedence_over_legacy_alias(self, reset_singleton):
+        """Should prefer the canonical env var when both env vars are set."""
+        os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "0.25"
+        os.environ["TUSK_SAMPLING_RATE"] = "0.1"
         instance = TuskDrift.get_instance()
 
         result = instance._determine_sampling_rate(None)
@@ -150,7 +178,7 @@ def test_uses_env_var_sampling_rate(self, reset_singleton):
     def test_init_param_takes_precedence_over_env_var(self, reset_singleton):
         """Should prefer init param over env var."""
         os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
-        os.environ["TUSK_SAMPLING_RATE"] = "0.25"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "0.25"
         instance = TuskDrift.get_instance()
 
         result = instance._determine_sampling_rate(0.75)
@@ -160,7 +188,7 @@ def test_init_param_takes_precedence_over_env_var(self, reset_singleton):
     def test_invalid_init_param_falls_back_to_env_var(self, reset_singleton):
         """Should use env var when init param is present but invalid."""
         os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
-        os.environ["TUSK_SAMPLING_RATE"] = "0.25"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "0.25"
         instance = TuskDrift.get_instance()
 
         result = instance._determine_sampling_rate(2.0)
@@ -190,10 +218,10 @@ def test_defaults_to_1_0(self, reset_singleton):
 
         assert result == 1.0
 
-    def test_rejects_invalid_env_var_sampling_rate(self, reset_singleton):
-        """Should reject invalid env var and use default."""
+    def test_rejects_invalid_recording_env_var_sampling_rate(self, reset_singleton):
+        """Should reject an invalid canonical env var and use default."""
         os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
-        os.environ["TUSK_SAMPLING_RATE"] = "invalid"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "invalid"
         instance = TuskDrift.get_instance()
 
         result = instance._determine_sampling_rate(None)
@@ -203,7 +231,7 @@ def test_rejects_invalid_env_var_sampling_rate(self, reset_singleton):
     def test_invalid_env_var_falls_back_to_config_file(self, reset_singleton):
         """Should use config file when env var is present but invalid."""
         os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
-        os.environ["TUSK_SAMPLING_RATE"] = "invalid"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "invalid"
         instance = TuskDrift.get_instance()
         instance.file_config = TuskFileConfig(
             recording=RecordingConfig(
@@ -215,6 +243,17 @@ def test_invalid_env_var_falls_back_to_config_file(self, reset_singleton):
 
         assert result == 0.4
 
+    def test_invalid_recording_env_var_falls_back_to_legacy_alias(self, reset_singleton):
+        """Should use the legacy alias when the canonical env var is invalid."""
+        os.environ["TUSK_DRIFT_MODE"] = "DISABLED"
+        os.environ["TUSK_RECORDING_SAMPLING_RATE"] = "invalid"
+        os.environ["TUSK_SAMPLING_RATE"] = "0.4"
+        instance = TuskDrift.get_instance()
+
+        result = instance._determine_sampling_rate(None)
+
+        assert result == 0.4
+
 
 class TestTuskDriftInitialize:
     """Tests for TuskDrift.initialize method."""
@@ -225,7 +264,13 @@ def reset_singleton(self):
         TuskDrift._instance = None
         TuskDrift._initialized = False
         # Clear environment variables
-        env_vars = ["TUSK_DRIFT_MODE", "TUSK_API_KEY", "TUSK_SAMPLING_RATE", "ENV"]
+        env_vars = [
+            "TUSK_DRIFT_MODE",
+            "TUSK_API_KEY",
+            "TUSK_RECORDING_SAMPLING_RATE",
+            "TUSK_SAMPLING_RATE",
+            "ENV",
+        ]
         for var in env_vars:
             if var in os.environ:
                 del os.environ[var]
diff --git a/tests/unit/test_sampling.py b/tests/unit/test_sampling.py
@@ -90,7 +90,7 @@ def test_rate_above_one_returns_none(self):
     def test_custom_source_in_warning(self):
         """Should include custom source in warning message."""
         # Just verify it doesn't raise with custom source
-        result = validate_sampling_rate(-0.5, source="env var TUSK_SAMPLING_RATE")
+        result = validate_sampling_rate(-0.5, source="env var TUSK_RECORDING_SAMPLING_RATE")
         assert result is None
 
     def test_converts_to_float(self):
