Calculation formulas for "Number of concurrent users", "System users" and "simultaneous online users"

The concepts associated with concurrent users include "number of concurrent users", "Number of system users" and "simultaneous online users", with a practical example to illustrate the differences between them.
Suppose there is an OA system with 2000 users-that is to say, the total number of users who may be using the OA system is 2000, the concept is "number of system users", which has an "online statistics" function (the system uses a global variable to count all logged-in users), From the online statistics function can be obtained, the peak of 500 people online (this 500 is generally referred to as the "number of simultaneous online"), then the number of concurrent users of the system?
According to our definition of the number of concurrent users, this 500 is the maximum number of business concurrent users used throughout the system. Of course, the value of 500 only indicates that 500 users logged in at the highest peak, not the actual server pressure. Because the pressure on the server is also related to the specific user access mode. For example, in these 500 users who "use the system simultaneously", consider a point in time at which 40% of the users are more interested in viewing the system announcement (note: "See" This action will not incur any burden on the server), 20% The user fills in the complex form (to the user fills in the form, only then will send the request to the service side in the "Submit" time, the filling process is not to the service side to constitute the pressure), 20% partial users in the daze (that is what also did not do), the remaining 20% users continuously from one page jumps to another page-- In this scenario, it can be said that only 20% of users really pressure the server. Therefore, as can be seen from the above example, the actual pressure on the server depends not only on the number of concurrent users, but also on the user's business scenario.
In the actual performance testing work, the tester is generally concerned about the number of business concurrent users, that is, from the business perspective should be set how many concurrent number is reasonable, so in the later discussion, is mainly for the number of business concurrent users to discuss, and, for convenience, The number of business concurrent users is referred to directly as the number of concurrent users.
(1) Calculate the average number of concurrent users: C = nl/t
(2) Peak number of concurrent users: C ' ≈c+3 radical C
In the formula (1), C is the average number of concurrent users; n is the number of login sessions; L is the average length of the login session; t refers to the length of the period of the visit.
The formula (2) gives the method of calculating the peak number of concurrent users, where C ' refers to the peak of the number of concurrent users, and C is the average number of concurrent users in the formula (1). The formula is derived from the assumption that the login session of the user is estimated to be in accordance with the Poisson distribution.
Instance:
Suppose there is an OA system, the system has 3,000 users, an average of about 400 users per day to access the system, for a typical user, the average user from logging on to exit the system in a day is 4 hours, in a day, the user only within 8 hours to use the system.
According to the formula (1) and the formula (2), you can get:
C = 400*4/8 = 200
C ' ≈200+3* radical 200 = 242
F=VU * r/t
Where F is the throughput, VU represents the number of virtual users, R represents the number of requests per virtual user, and T indicates the time spent in the performance test
R = T/ts
TS for user think time
General steps to calculate think time:
A, first calculate the number of concurrent users of the system
c=nl/t F=RXC
B, statistics the average throughput of the system
F=vu * r/t rxc = VU * r/t
C, statistics on the average number of requests issued by each user
R=u*c*t/vu
D. Calculate the think time according to the formula
Ts=t/r
Defect detection Effectiveness percent dde=tdft/(TDFC+TDFT) x100%
Where: All defects found in the tdft= testing process (i.e. found by the Test team), tdfc= all defects identified by the customer (measured at a standard point after the delivery of the version, e.g., six months later)

Defect exclusion Validity Percentage dre= (TDCT/TDFT) x100%
Among them: all defects corrected in tdct= test, all defects found during tdft= test

Test case design efficiency percent tde= (TDFT/NTC) x100%
Where: tdft= all defects found during the testing process, number of test cases ntc= run

The following formula is more suitable for white-box testing
Feature coverage = Test function points/total number of test functions (function points) performed at least once
Requirement coverage = number of requirements validated/Total demand quantity (demand)
Coverage = Number of test cases executed at least once/total number of test cases to be executed (test case)
Statement coverage = Number of statements executed at least once/number of valid program code lines
Decision coverage = number of times the decision result was evaluated/total number of decisions
Conditional coverage = number of quantity/condition operation values at least once evaluated for the condition operation value
Decision Condition Coverage = quantity of the condition operation or the result of the decision is evaluated at least once/(total number of conditional operations + total of decision results)
Context determination coverage = Number of decision branches executed within the context and/(number of decision branches in context * context)
State-based context ingress coverage = Cumulative number of methods executed in each state/(number of States * Total number of methods in the Class)
Branch condition Combination coverage = number of branch condition combinations evaluated to/branch condition combinations
Path coverage = number of paths executed at least once/total number of program paths

Calculation formulas for "Number of concurrent users", "System users" and "simultaneous online users"