Demonstration using regtest.
0# getblockchaininfo
1  "chain": "regtest",
2  "blocks": 0,
3  "headers": 0,
Mine a block
0# getblockchaininfo
1  "chain": "regtest",
2  "blocks": 1,
3  "headers": 1,
Call invalidateblock
 0# getblockchaininfo
 1  "chain": "regtest",
 2  "blocks": 0,
 3  "headers": 0,
 4# getchaintips
 5    "height": 1,
 6    "hash": "06702ef73c7d8629294f8b6386646f888d60979932ba2ee45e3495d8f25006b5",
 7    "branchlen": 1,
 8    "status": "invalid"
 9  },
10  {
11    "height": 0,
12    "hash": "0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206",
13    "branchlen": 0,
14    "status": "active"
Call reconsiderblock
0# getchaintips
1    "height": 1,
2    "hash": "06702ef73c7d8629294f8b6386646f888d60979932ba2ee45e3495d8f25006b5",
3    "branchlen": 0,
4    "status": "active"
Header count returned by getblockchaininfo is now < # of blocks.
0# getblockchaininfo
1  "chain": "regtest",
2  "blocks": 1,
3  "headers": 0,