Information Technology Reference
In-Depth Information
LAN / WAN
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LAN / WAN
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Application security
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Applications
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Figure 14.8
Tier identification for a complex 3-tier application
a tier 2 activity. Other development teams might design the web home page server as
a logon function and some of the search/view application functions, basically a tier
3 activity. One design is not inherently better than the other. Each design requires
commensurate test planning.
We take the fi rst test planning step for 3-tier applications similar to our fi rst step
with 2-tier applications: Develop a separate strategy for each tier. Figure 14.9 shows
how these separate tier strategies might look.
The second test planning step for 3-tier applications also follows the second
planning step with 2-tier applications: Stack the tiers with a sandwiched tier-to-tier
connectivity layer. Also, following the 2-tier planning model, we will place the ap-
plication (third tier) on the bottom of the strategy followed by the security (second
tier) next followed by the end user (fi rst tier) on top. Figure 14.10 shows the com-
pleted second step in our 3-tier test planning.
The 3-tier test execution approach will be to complete the third tier testing fi rst,
the second tier testing second, and the fi rst tier testing last. As with the 2-tier testing,
test harnesses will probably be needed for the lower layer tiers to simulate/emulate
the tiers above for testing purposes. Any useful information that the developers can
glean from the testing harnesses about the design and coding of higher layers is an
added testing contribution to the project.
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