diff --git a/tests/test_config/.gitignore b/tests/test_config/.gitignore
new file mode 100644
index 0000000..ac19afe
--- /dev/null
+++ b/tests/test_config/.gitignore
@@ -0,0 +1 @@
+plyngent-edit-*.toml
diff --git a/tests/test_config/plyngent-bad.toml b/tests/test_config/plyngent-bad.toml
new file mode 100644
index 0000000..bbeb840
--- /dev/null
+++ b/tests/test_config/plyngent-bad.toml
@@ -0,0 +1,15 @@
+[providers.test1]
+preset = "closeai"
+access_key_or_token = "sk-1145141919810"
+
+[providers.test2]
+preset = "openai-compatible"
+
+[providers.test3]
+preset = "nanthropic"
+access_key_or_token = "sk-1145141919810"
+
+[providers.foo1]
+preset = "deepseek"
+access_key_or_token = "sk-1145141919810"
+convention = "anthropic"
diff --git a/tests/test_config/plyngent-empty.toml b/tests/test_config/plyngent-empty.toml
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_config/plyngent-invalid.toml b/tests/test_config/plyngent-invalid.toml
new file mode 100644
index 0000000..2a55b0c
--- /dev/null
+++ b/tests/test_config/plyngent-invalid.toml
@@ -0,0 +1,3 @@
+[providers.test1]
+preset = "openai"
+access_key_or_token = "sk-1145141919810
\ No newline at end of file
diff --git a/tests/test_config/plyngent-valid.toml b/tests/test_config/plyngent-valid.toml
new file mode 100644
index 0000000..6a9b15c
--- /dev/null
+++ b/tests/test_config/plyngent-valid.toml
@@ -0,0 +1,22 @@
+[providers.test1]
+preset = "openai"
+access_key_or_token = "sk-1145141919810"
+
+[providers.test2]
+preset = "openai-compatible"
+url = "https://www.example.com/v1"
+access_key_or_token = "sk-1145141919810"
+
+[providers.test2.models]
+"glm-5.2" = { text = true, image_in = false, image_out = false, audio_in = false, audio_out = false, video_in = false, video_out = false, cost_factor = 5 }
+
+[providers.test3]
+preset = "anthropic"
+access_key_or_token = "sk-1145141919810"
+
+[providers.foo1]
+preset = "deepseek"
+access_key_or_token = "sk-1145141919810"
+
+[providers.foo1.extras]
+convention = "anthropic"
diff --git a/tests/test_config/test_config.py b/tests/test_config/test_config.py
new file mode 100644
index 0000000..172d968
--- /dev/null
+++ b/tests/test_config/test_config.py
@@ -0,0 +1,99 @@
+import shutil
+from collections.abc import Mapping
+from pathlib import Path
+
+import pytest
+
+import plyngent
+from plyngent.config import (
+    AnthropicProvider,
+    ConfigFormatError,
+    DeepseekProvider,
+    OpenAICompatibleProvider,
+    OpenAIProvider,
+)
+
+
+@pytest.fixture
+def default_config_source(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(plyngent.config, "default_config_source", Path(__file__).parent / "plyngent-valid.toml")
+
+
+def test_read_default_config(default_config_source: None) -> None:
+    _ = default_config_source
+    config = plyngent.config.load()
+    providers = config.providers
+    assert isinstance(providers, Mapping)
+    assert isinstance(providers["test1"], OpenAIProvider)
+    assert isinstance(providers["test2"], OpenAICompatibleProvider)
+    assert isinstance(providers["test3"], AnthropicProvider)
+    assert isinstance(providers["foo1"], DeepseekProvider)
+
+
+def test_read_valid_config() -> None:
+    config = plyngent.config.load(Path(__file__).parent / "plyngent-valid.toml")
+    providers = config.providers
+    assert isinstance(providers, Mapping)
+    assert isinstance(providers["test1"], OpenAIProvider)
+    assert isinstance(providers["test2"], OpenAICompatibleProvider)
+    assert isinstance(providers["test3"], AnthropicProvider)
+    assert isinstance(providers["foo1"], DeepseekProvider)
+
+
+def test_read_empty_config() -> None:
+    config = plyngent.config.load(Path(__file__).parent / "plyngent-empty.toml")
+    assert isinstance(config.providers, Mapping)
+    assert not config.providers
+
+
+def test_read_bad_config() -> None:
+    config = plyngent.config.load(Path(__file__).parent / "plyngent-bad.toml")
+    assert isinstance(config.providers, Mapping)
+    assert not config.providers
+    assert isinstance(config.bad_providers, Mapping)
+
+
+def test_read_invalid_config() -> None:
+    with pytest.raises(ConfigFormatError):
+        _ = plyngent.config.load(Path(__file__).parent / "plyngent-invalid.toml")
+
+
+def test_write_new_config() -> None:
+    file = Path(__file__).parent / "plyngent-edit-1.toml"
+    file.unlink(missing_ok=True)
+    config = plyngent.config.load(file)
+    assert isinstance(config.providers, Mapping)
+    config.providers = {
+        "foo1": OpenAIProvider(access_key_or_token="sk-00301212"),
+        "foo2": DeepseekProvider(access_key_or_token="sk-00301212"),
+    }
+    assert isinstance(config.providers, Mapping)
+    config.write()
+    assert isinstance(config.providers["foo1"], OpenAIProvider)
+    assert config.providers["foo1"].access_key_or_token == "sk-00301212"
+    assert isinstance(config.providers["foo2"], DeepseekProvider)
+    assert config.providers["foo2"].access_key_or_token == "sk-00301212"
+    config.reload()
+    assert isinstance(config.providers["foo1"], OpenAIProvider)
+    assert config.providers["foo1"].access_key_or_token == "sk-00301212"
+    assert isinstance(config.providers["foo2"], DeepseekProvider)
+    assert config.providers["foo2"].access_key_or_token == "sk-00301212"
+
+
+def test_update_config() -> None:
+    file = Path(__file__).parent / "plyngent-edit-2.toml"
+    _ = shutil.copy(Path(__file__).parent / "plyngent-valid.toml", file)
+    config = plyngent.config.load(file)
+    assert isinstance(config.providers, Mapping)
+    config.providers = config.providers | {"foo2": DeepseekProvider(access_key_or_token="sk-00301212")}
+    assert isinstance(config.providers, Mapping)
+    config.write()
+    assert isinstance(config.providers["foo1"], DeepseekProvider)
+    assert config.providers["foo1"].access_key_or_token == "sk-1145141919810"
+    assert isinstance(config.providers["foo2"], DeepseekProvider)
+    assert config.providers["foo2"].access_key_or_token == "sk-00301212"
+    config.reload()
+    assert isinstance(config.providers["foo1"], DeepseekProvider)
+    assert config.providers["foo1"].access_key_or_token == "sk-1145141919810"
+    assert isinstance(config.providers["foo2"], DeepseekProvider)
+    assert config.providers["foo2"].access_key_or_token == "sk-00301212"