software development life cycle(SDLC) covers the

Information gathering
Analysis
Designing
Implementation 
 a) coding
 b) Testing
Maintenance.
In this SDLC Implementation can come along with both 
coding as well as testing.

Software testing life cycle(STLC) covers 

Information gathering
Analysis
Designing
Testing
1. Test planning

2. Test development 

3. Test execution

4. Result analysis

5. Bug reporting
Maintenance.

In STLC we never come along with the coding(Developing)
section.we start it from requirment,analyse,design and 
testing.which will satisfy the customer requirment and
then we will deliver a quality product.