fix typos and grammar in docs

Signed-off-by: Jie Ma <jienius@outlook.com>

TESTING.md

@@ -28,7 +28,7 @@ Most code changes will fall into one of the following categories.
 ### Writing tests for new features
 
 New code should be covered by unit tests. If the code is difficult to test with
-a unit tests then that is a good sign that it should be refactored to make it
+unit tests, then that is a good sign that it should be refactored to make it
 easier to reuse and maintain. Consider accepting unexported interfaces instead
 of structs so that fakes can be provided for dependencies.
 
@@ -44,12 +44,12 @@ case. Error cases should be handled by unit tests.
 
 Bugs fixes should include a unit test case which exercises the bug.
 
-A bug fix may also include new assertions in an existing integration tests for the
+A bug fix may also include new assertions in existing integration tests for the
 API endpoint.
 
 ### Integration tests environment considerations
 
-When adding new tests or modifying existing test under `integration/`, testing 
+When adding new tests or modifying existing tests under `integration/`, testing
 environment should be properly considered. `skip.If` from 
 [gotest.tools/skip](https://godoc.org/gotest.tools/skip) can be used to make the 
 test run conditionally. Full testing environment conditions can be found at 
@@ -104,9 +104,9 @@ TEST_SKIP_INTEGRATION and/or TEST_SKIP_INTEGRATION_CLI environment variables.
 Flags specific to each suite can be set in the TESTFLAGS_INTEGRATION and
 TESTFLAGS_INTEGRATION_CLI environment variables.
 
-If all you want is to specity a test filter to run, you can set the
+If all you want is to specify a test filter to run, you can set the
 `TEST_FILTER` environment variable. This ends up getting passed directly to `go
-test -run` (or `go test -check-f`, dpenending on the test suite). It will also
+test -run` (or `go test -check-f`, depending on the test suite). It will also
 automatically set the other above mentioned environment variables accordingly.
 
 ### Go Version

docs/contributing/test.md

@@ -83,7 +83,7 @@ hour. To run the test suite, do the following:
     * cross-compiles all the binaries for the various operating systems
     * runs all the tests in the system
 
-    It can take approximate one hour to run all the tests. The time depends
+    It can take approximately one hour to run all the tests. The time depends
     on your host performance. The default timeout is 60 minutes, which is
     defined in `hack/make.sh` (`${TIMEOUT:=60m}`). You can modify the timeout
     value on the basis of your host performance. When they complete
@@ -208,7 +208,7 @@ run a Bash terminal on Windows.
     ```
 
 4.  Set `DOCKER_TEST_HOST` to the `tcp://IP_ADDRESS:2376` value; substitute your
-    Linux machines actual IP address. For example:
+    Linux machine's actual IP address. For example:
 
     ```bash
     $ export DOCKER_TEST_HOST=tcp://213.124.23.200:2376